I currently have a radeon 5850 that I may consider upgrading to a gtx 580. However I also have thoughts of just adding on another 5850 if I overhaul my system all together as im using a motherboard from an even older system (p35-ds3l). Im currently running a q9550 and I would like to upgrade to an i7-950 (230 @ microcenter) coupled with a msi big bang motherboard.
So basically I am looking at either
A)changing to a different socket 775 mobo with more stable cpu power for higher oc on q9550 + crossfire ability. ~500 USD
B) overhauling entire system including ram, power supply, video card, processor, mobo, and a case. ~2k USD
This upgrade would last me for a year+ most likely if I dont get impulsive as well as increase my capabilities of running multiple copies of vmware and maxing out video games @ my current resolution of 1920 x 1200. The real question is whether this investment may be worth the cost now or if im better off waiting for cyber monday/black friday.
1) That $230 microcenter deal is a great one.
2) The MSI big bang motherboard is very expensive, considering you can do about as well with a $200 motherboard like the asus sabretooth. The advantage of X58 is that you can get more ram, up to 24gb for vm machines.
3) I would not invest more on a 775 based system. Plan on selling the parts off.
4) With sandy bridge launch(jan 9 rumored) I think I would wait for that.
5) On a single monitor @ 1920 x 1200, the GTX580 should be able to run anything well. If you are looking at triple monitor gaming only then should you be looking at sli. I would do the GTX580 now, and see how you do.
6) ATI high end cards are delayed to december. Only then might there be price pressure on the GTX580 cards.
My 2 cents. The 5850 was never a high-end card so why would you need one now? Investing on a LGA775 system might be wasteful now unless you get a really great deal somewhere like finding a used Gigabyte EP45 board that support XFire in x8x8 for about ~50$ then adding a 2nd 5850. Otherwise I think your best bet might be to wait for Sandy Bridge since it will introduce new sockets.