The 5870 is pretty much twice as fast as a 5770.
Originally Posted by SAFX
Newegg had an ETA of today (11/23) for availability on the Sapphire Radeon 5870, but unfortunately, today came and went and no 5870, and no place right now has this card available for under $409.
I am now thinking of just picking up a 5770. It's a huge upgrade from my GTX 8800. How much of a performance difference is there between the 5770 and the 5870?
Originally Posted by iandh
Another thing to consider is that if you go 5770CF, you have no upgrade path other than selling your cards and buying new ones. If you go 5870, you can add a second later down the road.
5870 is also more like to hold resale value for longer.
Originally Posted by Mygaffer
If his board supports it, he could always go tri-fire, though of course scaling won't be as good.
Of course if he is gaming at 1920x1080 or above and with AA enabled then he'll want the larger frame buffer and memory throughput like you've stated. I know the 5870's are hard to find but I think it is worth it to keep plugging away, or wait for availability to get better and the prices to drop to more reasonable levels.
I just saw what monitors you are using, and I firmly recommend holding out for a 5870.