Currently emulators don't need dx8. There are no games that currently require it (as far as I am aware) and only very new graphics cards (eg geforce 3) support the new features that they added. It probably won't hurt to upgrade but it probably won't make any difference either.
DX 8 works fine for me. I always try to get the latest version. It works w/all my emulators and PC games as well. The only thing I am not sure about is if I have DX 8.0a or not. When I downloaded what was supossed to be DX 8.0a form Micro Soft, the download was exactally the same as DX 8. I don't even see evidence of it saying 8.0a anywhere. Could someone tell me where they got their version of DX 8.0a from? Please. I want to make sure that it get DX 8.0a this time, not just DX 8 again. Thanks.