That SP means it's overclocked and is around as fast as the GTX 280. I thought about getting a Sapphire Toxic HD 4870 (overclocked) which would also put it mostly within GTX 280 territory.
But...... 2 things why I have to stick with the ATI...... My pc components are mostly AMD*. I have noticed with my last (AMD) pc that the GF 8600GT was prone to several BSOD's in the past while my X800XL peformed superbly without a single crash/lockup in XP, Vista, and Win 7 RC.
Besides, I alternate between ATI and nVidia with every video card acquisition. Since my last one was an 8600GT....... It's ATI this time around. I've never broken the pattern (even if there's a performance and cost disadvantage).

Superstitious? Yup. It sure is. Ha Ha!
Mach 64 (plus Matrox Millenium)---->Riva 128---->3dfx Voodoo---->3dfx Voodoo2 SLI. Post 3dfx.... TNT2---->Radeon---->GF4-Ti4200---->X800XL---->GF 8600GT----> HD4870?
Using stock, unoverclocked cards, an HD 4870 1gb is around $40 cheaper and slightly quicker than a GTX 260. Even an overclocked HD 4870 is still cheaper than an overclocked GTX 260 by $10-$30.
*Much like what I suspect with MS apps/games vs 3rd-party ones in different versions of Windows. The MS apps/games worked like a charm even without ever being patched.