Upgrading for 4870(512)s in crossfire to 5870 worth it?

It's probably not worth the upgrade. It would yield similar performance at 1680x1050 or lower. If you play at higher resolutions, you may be able to justify it for the larger VRAM. You'd also get eyefinity, dx11, ect with the 5870. What resolutions do you play at? What games?

1920x1200 and the games i play are wow,LFD,LFD2, crysis, crysis warhead, dragon age, etc......mostly the new games atm...

At that resolution, you'd defiantly benefit from the full 1GB of VRAM. I'm not sure if the improvement would be worth the $400. I'll look around for some benchmarks. Are you having trouble playing at the settings you want right now?

A 5870 would also use less energy and produce less heat if that matters to you.

For that price, I wouldn't. Not unless you're unhappy with the way your games are running now. I'd wait until DX11 becomes more widespread, at which point you'll probably be able to get an even better card than the 5870.

Energy savings is nice but, not 400$ nice  . Yeah the vram is what I really is important at that rez. I wish I had gotten the 1g cards then, I probably wouldn't be even thinking of a upgrade... maybe I should try 2 4890's? maybe more of an performance increase? or 2 5770's? I wouldn't mind doing 2 5850's in xfire but thats 600 plus....dont want to go over 400us....

I have a single 4890 and it plays all my games at max or near max settings, but I'm only at 1680x1050. I'm not sure if you'd need 2 4890's for 1920x1200, and you wouldn't get dx11, eyefinity, or the efficiency. If you get 2 5770's you won't have anywhere to upgrade in the future. You could get one 5850 now and grab another one later, but you'll probably decrease your FPS with a single 5850. Unless you don't feel your 4870's are doing what you want, I wouldn't worry about it.

If you sold your 4870's on ebay, you might be able to get $150 a piece for them. That would make the 5870 only a $100 upgrade.

Don't forget about much less power consumption, less noise and heat with the 5870.