I have an I5 3570k over clocked to about 4.2 ghz. I was using 8 gigs of ram but had a bit too much lag. When I upgraded both my video card (from 2gigs to 4 gigs) and my ram from 8 gigs to 16g, I have found play just find. My turn times after 250+ turns is about 15 to 20 seconds depending on Zoom level I have at that time. 

I only play on Insane maps and I play with NO less than 30 majors and abundant Minors. 

I suspect it is the RAM alone.  I have an i7, 8G RAM, and NVIDIA graphics with 4G, and I lag on immense like you do.

My desktop has an Intel i7 4790k 4.0GHz CPU, 32GB of RAM and a Nvidia GeForce GTX 980 4GB GPU and I don't get any lag on insane maps. But my laptop has an Intel i5 3317U 1.7GHz CPU, 8GB of RAM and a Nividia GeForce GT 620M 1GB GPU and even though it is below the minimum specs it runs all map sizes up to Gigantic fine. Anything higher and it starts to lag.

Mass annihilation simply for the sake of shorter turn times, have you no shame? 

Seriously, that is interesting information.  It helps me understand my much more modest rig and what I can expect and do with it.  I had already done the 16 gig of ram, and that made a bunch of difference.  The rest would require a rework from the motherboard on up. 

To me, it shows that Stardock has made the software as flexible as possible about its workload along with other software tricks I wouldn't ever recognize.  The performance issues are demonstrably a big priority and consideration.  This is good, because what they have done with the extreme sizes and faction counts is an ambitious effort and will strain all current day rigs under the right settings.   They have future-proofed the game in an interesting way.  I have high hopes that future optimization passes will have incremental but appreciable efficiency buffs.  There is a lot of thought hidden under all the space battles and planet screens.  It gives me a certain level of anticipation for someday when I get a full built rig for my birthday or something.