Want to upgrade GPU for best price

[elidril]

My Current Setup:

Intel Core I5-2400 3.1 ghz

XFX HD-687A-ZHFC Radeon HD 6870 1GB 256-Bit GDDR5

ASRock Z68 Extreme3 Gen3 LGA 1155 Intel Z68 Motherboard

CORSAIR Vengeance 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600

CORSAIR Enthusiast Series TX650 650W ATX12V/EPS12V 80 PLUS BRONZE Certified Active PFC High Performance Power Supply

Want to upgrade GPU on a small budget. Realize that there isn't any gpu's in my price range right now that would be a significant upgrade. Considering buying a second 6870 and running Xfire. Will this show significant gains? Can my power supply handle it?

Do you need to run two of the same cards for crossfire....ie 2 6870's or even two of the same manufacturers cards?

Thoughts on purchasing a used video card via ebay or something from a reputable seller with good feedback?

Thanks guys.

 

[clutchc]

In the past, I would have persuaded one to avoid CF with that class of card due to bad micro-stutter issues when paired up. But with AMD's new line of drivers with Frame Pacing, the m-s issue is pretty well taken care of from my experience. Your PSU's +12V rail has the amp capacity and Wattage (636W) to handle 2 of those cards (151W @ 12.6A on the +12V rail(s) per card)... but it only has 2 x 6/8 pin cables. And it would not have a lot of headroom left over. For that reason, I would probably suggest going to a faster single card. Besides, the only HD 6870s available now are probably all going to be used.

I realize you mentioned that funds were tight right now. Can you offer a budget that you are willing to spend?