I didn't mean to sound harsh or anything, but if you read your origional post, it does seem like you are a bit unsure as to your decision. That's why I thought you were guessing. Also, BAT and Parasound are very different sounding products, in general. That threw me off as well.
The upside to this is that you shouldn't have any trouble at all getting the amp and the preamp to work together from a technical standpoint. As far as sound quality goes, you'll probably be very happy, as well. I've always felt that the preamp is the most overlooked component in most peoples systems. If you don't get it right its just one problem after another. In your case, the BAT will probably be the strongest component in the system. That's a very good thing. Everything should get better: imaging, resolution, transparency, dynamics should all be enhanced from what they now are. I think you will be surprised at just how big the difference will be.
The upside to this is that you shouldn't have any trouble at all getting the amp and the preamp to work together from a technical standpoint. As far as sound quality goes, you'll probably be very happy, as well. I've always felt that the preamp is the most overlooked component in most peoples systems. If you don't get it right its just one problem after another. In your case, the BAT will probably be the strongest component in the system. That's a very good thing. Everything should get better: imaging, resolution, transparency, dynamics should all be enhanced from what they now are. I think you will be surprised at just how big the difference will be.