I hope this is the right place to ask my questions.

I've got some problems with my Radeon HD 5770 and 3D games under WINE:
missing Parts of faces and/or equipment in some Games (e.g. X-the threat, lineage 2)
invisible units in some strategy games (e.g. Star Wars - Empire at War)
and complete System freezes (e.g. with Lineage 2)

I'm using the proprietary ATI graphics driver, Kubuntu 10.10 and Wine 1.3.10

In the Wine community, they told me that the probably only way to get rid of those bugs is to get a nVidia card. Are they right or is there a chance to get my ATI card working properly?
If they're right, which nVidia card would you suggest to replace my 5770?
And is replacing my ATI Card with a nVidia one helpful or will I just replace one problem with another one?

Thank you for your help!