I've got the same, so I'm also interested in the answer.  I know large works, and I suspect huge will too, but insane?

16 gb on the largest one running fine.

Fps cut in HALF, from 60 to 31.

Time between turns varies heavily.

Occasional stutter.

More than likely because im too stubborn to turn down my graphics settings, actually it would probably stop lagging if I zoomed out. Take that as you may.

And I have 8GB and cannot even start on Insane

I just bought the game 2 days ago so I'm not really sure what's going on.

I will try messing around with the virtual memory this evening and see if that helps

(GalCiv 3 is installed on my  SSD with about 50 GIG free space

Any pointers on what are the  best settings for the virtual memory in case of problems with the big maps?

It has to deal with the number of calculations the computer can do per second.

Although there are more optimizations added all the time by release 8 should do.

Unless you are trying to make a 100 player game on an insane map.

Then I would suggest 16.

How many max players/races on an insane map is safe to use, when limited to 8 gigs of Ram?

Also, I have a PHENOM 2 Quad core running at 4Ghz, and a  R9 270 with 2gb Ram video card.

Well...I do, and I don't have any real big problems, even with all the graphic eyecandy on. Sure you have some slowdown in late game between turns, when all standard factions are still growing strong, but nothing that makes it impossible to play.

I upgraded from 8GB to 16GB and I've seen a huge increase in performance on the 3 largest map sizes.

Worth it if you want to play on Insane. I found 8GB played on Gigantic pretty well.

well my computer definitely needs upgrades but i can load insane but it won't play very well (removed fow via console just to see how it might go). I have 8 Gb ram and the rest of my computer is ancient top of the line(2008). A Q9550 processor, 790i ultra sli mobo, 128gb ssd. I usually go with Huge galaxy and it goes quite well, This is the first game that is going to make me rebuild my whole computer mainly due to the max 8gb ram of my mobo. Really wish i could get more ram without a new mobo also requiring a new cpu, just how it goes sometimes   , the fact that my PSU is half ide half sata says something about it's age.

I have my page file on my secondary regular hard drive, the size or placement of it doesn't seem to affect the performance too much(tried it on my ssd, the lack of performance increase made me put it back on the rotating drive). In both cases i put it to 8gb min and 16gb max. RAM ftw! (hence the coming upgrades...)

just an afterthought, my comp is basically ancient however still viable but given the time frame it has gone through several irl events so others might have a better 'solution' for you if yours has been better taken care of(i have random freezes nowadays, not so much since i secured the graphics card, not sure how it wasn't) I hope possibly this helped you at all, i am typically quiet sober so there you go.