Since the prices of the 5870's have dropped I'm debating whether or not to pickup a second one and crossfire with the one that I already have or pickup a GTX 260 for physx. I have heard that the 5870's do not scale well in crossfire and the price difference is about $130 more for the 5870 than the GTX 260. Overall I'm just looking for opinions on which would be a better or more noticable move.
Primary system specs are below:
Mobo: Asus M3A32MVP-Deluxe
CPU: AMD Phenom II x4 955 @ 3.41Ghz
RAM: 8GB G-Skill DDR-2
Graphics: Sapphire 5870 Vapor-X @ 900/1300
Power Supply: Kingwin ABT-1000MA1S 1000w power supply
OS: Windows 7 Home Premium
If you don't play games that use PhysX it would be a waste. Plus you would need to get the driver tweak to use it for PhysX and all that mess. It is up to you. The card will just sit there waiting for PhysX stuff, consuming power at idle.
A 2nd 5870 scales really well, from what I know. However, Hell_storm has a good point. Sell off the 5870 and get the next gen best single card. Look at it's performance when it comes out and compare that to a 5870 CF setup then make a choice. Dual card setups can be a headache because of heat. I've been there, will never go there again. You need alot of airflow over the cards and good case exhaust.
Who wants to deal with the drama of a driver hack?! We have to deal with driver issues anyhow. Imagine the headache a hack would add!?
I say go for the 5870. I'm running with 3 5850s and they pretty well rock. Since I can crank all settings to the max (I actually could do this with 2 cards), I have sworn off the 6xxx series. Two 5870s should more than suffice. The additional cards actually clock down by default when not in use.
Jay2tall is right about the heat. These things can throw heat. I do have a case that's extremely air-flow friendly. I have nine fans blowing air around. I've never had a problem with heat issues. I'm not saying you need this much airflow, but I'm sure it makes the multi-card heat situation negligible in my case. The Gigabyte 5850 and 5870 cards have great cooling solutions on them though. My Gigabyte 5850s are factory OC'd a bit and run about 10C cooler than my standard-clocked HIS.
You could sell that 5870 and buy yourself a 580 or 570 (depending on your budget) and you get the f... lot - phizzzycs, nvidia drivers(rock solid) and you don't need extra airflow.
Best of luck out there !