B&W Speaker Selection Help-Maybe Amp help

I have 804 matrix, HTM center channel and THX-SCM8 B&W speakers for my threater system. I have $2000 to spend and am looking for advice on upgrading my speakers. I want to stay with B&W and am evaluating N804's and an nautilus HTMI center channel. Which one to upgrade? Also have a Denon ARV4800 amp. Maybe I should just update the amp> I'm a novice audiophile who really appreciates the sound but technically not up to speed on selections.