If you're going to use a configurator, I would recommend these guys
, if possible. I've built my last couple of systems myself, but I used them once upon a time, and I had no real regrets; just that I didn't know enough about computers then to know how shoddy of a system I built. I never had need of support from them, but I never doubted they'd be there, either. I can't say the same for ibuypower-I haven't dealt with them myself, and don't ever want to, but there are plenty of horror stories about them out there. It also helps that pcusa won't overcharge you -quite- as much (hey, they still need to make a profit, too).
They seem to have removed their barebone options, but in any case, there are a number of "kits" to customize, most notably this one.
They don't specify what brand the RAM or hard drive(s) are, but I verified the PSUs are solid. I can't seem to easily find specs on the 500W, so I'd do the 650W personally, as it's only $6 more than the 600W. (The first few, that aren't exactly named-they're NspireGear, and apparently designed to be server power supplies. The latter two have at least 26A on the 12V rail[s], so you should be good to go.) I'd probably be more comfortable with a ~500W FSP myself, but if you don't want to have to install it yourself, that's the best option.
Interestingly, the GA-P35-DS3L is there, and at only $20 more than the default board. 2GB of 800MHZ DDR2 over the default 512MB selected for you adds around $60 total, which isn't bad. Either the 320GB or the 500GB hard drive is a good deal, replacing the default selected 80GB, at $78 or $100 respectively. The only real burner selection with a secondary DVD-ROM will run you about $40 together.
Admittedly, the problem here is video card selection, again. The 8600GTS is only $30 more than the 1GB 8600GT there, but then the 9600GT is only $20 more than that. 9600GT is technically superior to the 256MB 8800GT, but not the 512MB 8800GT, which are about $25 and $50 more than it respectively. It's really up to you (or whoever's funding this upgrade, anyway) where to stop, but I'd say you won't be getting your money's worth without at least an 8600GT (and the 512MB is the only one I see listed there).
And XP Home is about $85 there as well.
I'm questioning whether you have your heart set on the E6750, as for a game like GCII (or most games, really), the video card is simply more important. You could tone it down to the E2180 or the E4500 and save some cash to spend on your video card. As the E2xxx series only has 1MB of L2 cache, they are a bit slower than their more muscular brethren, but the vast majority of users won't notice a difference between the 2MB L2 cache the E4xxx series has and the 4MB L2 cache the E6xxx series offers. The E4500 is $40 more than the E2180, and the E6750 is $70 more than the E4500, so there's some room there, depending on your personal preference. Cache really doesn't matter as much as people would like you to believe-but it the difference between 1 and 2 is far more significant than that between 2 and 4 (counterintuitive, maybe, but true).
Alternatively, you could use the integrated configurator here
and save about $30 off the bat on an 8600GTS (how about this one
, which has a $40 mail-in rebate attached to it), possibly saving some on the motherboard as well. The board itself is less of a concern if you're going to be replacing the integrated with a dedicated card anyway, but I'd still recommend anything that says 7050/7100 or 1200 rather than G31/G33. Other than that, the choice is pretty much up to you, though, again, I'm partial to Gigabyte.
All said and done, you could probably save a good ~$200 by following all of my suggestions, so if you follow even some of them, you should be good to go. I do notice that, at least in that configurator, ibuypower will not allow you to select no video card, even though the board has integrated. (Even THEY know how crappy Intel's integrated is! Sorry, couldn't resist.)
I'd almost suggest that you get your own RAM as well, rather than letting the configurator company decide for you, but it wouldn't save you any money; probably about $5-$10 more overall (since you can't select no RAM in the configurators, either), but you'd wind up with a better system overall, so up to you. I got these guys
for a friend of mine, and he hasn't complained yet. They're not quite up to my Micron D9GMH, but they'll handle anything he throws at them and then some, even if he decides to overclock them eventually.
As an FYI, installing RAM, or a video card, if you haven't done it before, is insanely simple. It's almost plug and play. And fortunately, it doesn't void your warranty, either. (If they tell you it does, they're crazy. Adding/replacing RAM doesn't even void laptop warranties, and the only reason video cards aren't included in that is because it's next to impossible to get your hands on an actual video card for one, or they would be as well.) That said, just because it's insanely simple doesn't mean you shouldn't be careful-whether it's the first time you've done it or the thousandth. That's how I broke my SATA hard drive, but that's a story for another day.
Of course, all of the links I've provided are contingent on you being in the U.S., but since you posted ibuypower, I'm betting that's a safe assumption. Please do correct me if I'm wrong, so I can make more valid suggestions.
As for the monitor...either get one at a local electronics store (Staples/Circuit City/Office Depot/etc) or browse around on Newegg/TigerDirect (ZipZoomFly is good as well but I can't stand their interface even more than TD's); whatever you find in any of those places will be superior to whatever "bundled" monitors the configurators make available. Again, unless you've already got the monitor, in which case, there's really nothing to do but move on to the next component, is there?
Someone else can probably give you a better explanation of the power supply issue than I can, but the long story short is the video card and the CPU, which consume most of your power, are going to be pulling the vast majority of their power from the 12V rail (think of it as a segment) of the PSU. A 1000W PSU is useless if it only has 10A on the 12V rail. An extreme example, but valid nonetheless. Ideally, you don't want to be over about 80% of the PSU's max load-either on a single rail (since most PSUs actually only have one 12V rail, even when they split them, we're treating the 12V as one), or as a whole, which leads to the practice of getting a PSU that has more capacity than you need. It'll only pull from the wall what's needed, though, so a larger PSU isn't necessarily going to wind up increasing your electric bill (except for the fact that past a certain point, the efficiency does tend to drop a bit, but there are ongoing efforts to make the minimum efficiency 80%, which are already helping).
I'm dehydrated. I'm going to go get a drink.