My trusty 9800GTX 512mb died on me yesterday. On windows XP, where you get +20% performance in dx9 apps, I could run anything and everything cranked.
I'm back on an 8600GTS 256mb now but mostly playing indies like dominions 3, battles of norghan, dungeon crawl stone soup and a tiny bit of Wyvern for an oldschool laugh. Also, heroes of newerth runs fine.
So, since I'm in the market as well I thought I'd post what I took away with me from my brief hunt. I'm really in no rush.
9800GTX(aka gtx240) max power draw 170 watts, 70GB/sec BW, 256bit bus, 512MB, 675MHz gpu
($200)GTX460 160 watts, 115GB/s, 256bit bus, 1GB, 675MHz gpu
($500)GTX580 240 watts, 192GB/s, 384bit, 1GB, 772MHz gpu
edit: See
http://www.gpureview.com/show_cards.php?card1=632&card2=559 for more cards and to compare two side by side. Fantastic resource, this site.
Bare in mind that the 9800GTX is more powerful than the current generation consoles. If something is going to release with a console version your 9800 rig will be able to run it better at high resolutions.
DX10 was a no show. Sure, I never left XP. Did I miss anything though? Nope. I see DX11 going much the same way with titles running exclusively on a dx11 renderer being extremely rare. ~33% of the pc market is still dx9, after all and xbox uses a modified version of dx9.
Microsoft used to sell MS-DOS 5 patches in a box. Theres no reason dx11 couldn't run on xp they just wanted to sell everyone windows again. Then again and again, only getting you to upgrade because they drop support and force you to.
Pretty much until we see the DirectX box 1080 you won't need to take your graphics too high to be able to play most releases.
I'm probably going to hold off until Guildwars2 and dungeon siege 3 are released, try them on 8600gts, then upgrade to something with <= power draw of my old card so i dont have to grab a new PSU too.
ps. I've always gone with nvidia cards but theres probably a cheaper ATI card out there with a faster GPU for less green worth considering. A friend is very happy with a 5770 he got cheaply.