I think the results will start to improve when drivers get more mature and there comes games that can take full use of parhelia (&DX9).
When Parhelia drivers come available for AmigaOS4, I bet there is u13 technology available and Parhelias around 400Mhz... as well as some other new GFX cards.
Radeon8500 will be the 3D GFX card for my next Amiga. ;-)