I run on a intel core 2 quad, 2 gig ddr2 ram, Geforce 8800 GTO. Highest settings + 1650x1080 resolution = almost no slowdowns.
Knowing stardock's policies, they like to sell to low-end machines as well as high-end, their reason for doing so is because it is one of their anti-drm stands. If you target ONLY high-end machines, the people who paid the 6 grand for em (yea I know someone who did and I think they are absolutely nuts) are NOT going to be able to afford your game, so they will download it. Also they know what they are doing so they will have no fears about downloading and cracking.
So they target a wide audience who does not need to buy a new computer to just play their game.
Problem with performance of DG:
1) No use of multiple cores. I wonder if LUA uses an global interpreter lock... If it does they need to do multi-processing not multi-threading or they will NEVER get the advantages of multi-core CPUs which are standard now days in most home computers sold. This is especially true when they don't use multiple cores when you host a game, the game is slow even though I have 3 cores idle fully capable of executing the server portion of the game hosting.
2) The game is still in beta2. I do expect that the game will have significant performance improvements as once the major bugs are gone, they will start working on performance improvements as top priority. Obviously currently only the top notch machines can play DG at nice graphics settings.
3) I expect the game to be able to scale for a low-end machine, and for a machine even better than mine, so that a really high game setting will look amazing, but we can scale it down and it will still look alright. I would expect my machine to be in medium setings range.