personally, i'd (at least initially) keep the onkyo and your very good existing speaker config and get a three channel amp to power the fronts and center--perhaps something like a parasound or wyred4sound--i think you find signicancant improvement + save some $$. you can always change out pre/pro and/or add an additional amp later.
Moving From AVR to Amp
Relative newbie here so please excuse my lack of knowledge. I am assembling a system for HT and music (70/30 respectively). My room is 29x12, viewing/listening position is about 8-10 feet from the front speakers. I started a couple of years ago with Totem Forests, Model 1 center and Lynks rears, Velo SPL-1500R sub. in a 5.1 set up. I have been using an Onkyo TX-SR805 and a Squeezebox just to start while I gradually build my system. I recently added a media center PC built by a friend, that I use mainly for streaming movies and as a blu-ray player. I am thinking of (1) adding a separate multichannel amp (either 5 or 7 channel) and using the AVR as a pre/pro for a while, (2) getting a good stand alone DVD/CD player now, and then adding separate components in the next year or two. I am budgeting roughly $3,000-$4,000 (including interconnects) in this phase of the upgrade. Used but well cared for equipment is fine with me to maximize the value of my system. My questions, before I go listening/shopping: Is this a reasonable way to upgrade? Would I be better off selling the AVR and starting from scratch? What amps should I consider? Is it better to get a 5 channel amp for now and add a separate amp if I go to a 7.1 set up later? Sorry for the long post, but there seems to be alot of info to sort through and I am trying to learn.