Eyefinity upgrade help needed

[hfxmike]

I have a Powercolor PSC+ 5770 with an amdx4 635 - 3x1920x1080 displays. I want an 80% improvement in framerates. Only want to spend around $100. What is the best/cheapest/future-proof option?

1) buy another 5770 and xfire it
2) sell the 5770 and replace it with something like a 6870, 5870
3) other

My instincts tell me to sell the 5770 and put the money towards a 6870...then, down the road I can xfire that. xfiring 5770's is a dead end, but maybe good enough and cheaper? any advice welcome

thanks
ps - I would be buying used or on sale with rebates. No way I'm paying retail.
pps - how much can I get for my 5770?

[Stock]

A used 5770 will for $90-100 in good condition. I'm not certain on framerates for games, but in terms of pure performance when looking for an 80% upgrade @ $100, it's unrealistic. The closest you'll get to that figure with a single GPU is the GTX 580/ATI 5970. I recommend looking at one of the TPU charts. NVIDIA GeForce GTX 560 Ti 1 GB Review - Page 27/31 | techPowerUp

I would probably go with another 5770 for crossfire, or buy a used 5870 ($200) unless you want the latest generation... regardless though, 5870 > 6870.

[JJThomp]

Honestly if you can go for a 6950 they aren't too expensive and they perform pretty wicked you can get one for between $250-$275 for a 2gb and for eyefinity it should give you a lot better performance because the extra memory will help at high resolutions.

So if you can afford the $75 extra over the second 5770 thats my recommendation or I'd go even higher with the 6970.

if you can't afford it I'd be looking at the 5870 or 6870. 5870 is technically better except for tesselation but it'd more expensive.

Pretty much do anything but get another 5770 because like you said that's a dead end.