Your Pioneer will be fine.

Lots of people like both the Aperion and especially the Ascends (which I find very ugly). I heard some Aperion towers and liked them very much.

If your speakers are really only going to be 6' apart, you can probably get by without a center channel (using phantom mode).

You can get really great bookshelf speakers; if your room doesn't easily accommodate floor-standers, I wouldn't obsess about it.

Have fun!

bibere usque ad hilaritatem