About the only thing on a VGA that [kinda] matters for 2D speed, and we use 2D only in any DAW, is memory speed. The faster the memory - the faster the drawing, but the difference is negligible. That said, all 128bit memory bus VGA-s, even some 64-bit, have more than enough speed for 2D. The most important thing, I think, is the stability and compatibility of the VGA driver.
Conclusion: no, you don't need the best VGA card out there, only if you're a gamer. What you should be looking at is that it's passively cooled so you could "enjoy the silence" [Depeche Mode
]. I usually buy second from the top [in terms of speed] of the passively cooled ones and presently that's nVidia GForce7600GS or 8600GS.
Cheers!