How old is your computer? I don't think you will get a noticeable drop in performance with D3D if you have a decent computer.
Hard to explain, because I bought it and continuously upgraded it.
But the specs are...
Radeon HD 4550 512 MB
2 GB DDR (or DDR2, I forgot.)
2.0 GHZ Athlon Processor (forgot some of the specifics.)
And that's about all I can think of off the top of my head.
Games section?
I posted in the wrong one by accident...asdf.
don't use ATI
Even if I take my current graphics card out, it has an integrated ATI one, so no.
Buy Play CSS
I found it way too easy, even against players.