I think you might find more useful comment on AVRs at the website of our sibling publication, Home Theater (http://www.hometheater.com/), than here.  But, as for the speakers, the ideal center would, of course, be another Pioneer SP-BS41-LR (if you can buy just one) or the SP-C21 center in the same series.  Subs do not necessarily have to be "matched" to the main speakers, so the options are wide and issues of budget and size need to be defined.

Kal