The X800XL has no pipes to disable if thats the card you are wanting. It has all 16 pipes, which is a pro to the X800XL. The only negative to the X800XL is the lack of Shader Model 3, which is essential, but since you said your upgrading again before long anyways, it wouldn't be that big of deal.
I would recommend either the 6600 GT, or going for the X800XL or 6800 GT preferrably. Don't get a 12-piped card with the intent of unlocking the pipes.