How Important is the receiver vs separates in HT?

I'm in the process of significantly upgrading my HT system.I haven't been serious until now.My first step is to upgrade my receiver.Next I will upgrade my speakers.The system will be used for 100% HT. After looking at numerous flagship Japanese receivers especially the Denon 5803 and the Pioneer 47&49TX,I am about to make the decision to buy the new B&k 507. My thinking is that the processors in all these units must be very similar. Also with the post proceesing being THX ultra 2 in all the models I am guessing I shouldn't notice much difference there. Does anyone disagree with my thinking re the processing of these models? I am leaning toward the new B&k because of it's amplifier.I'm told, but am not sure, the B&k has a better(bigger) power transformer and more Mosfet amplifiers per channel than any of the Japanese receivers.Also that the B&K is more open and less harsh sounding.Do you agree?? The only hestitation I have (so far) is that people with Lexicon's Logic7 keep telling me it's processing ability "blows away" DPL2 and DD-Ex and even DTS-Es.Is that true in your experience and if so is it worth the huge difference to buy the Lexicon Mc12 + an Amp?I will be running a system with 2 sides and 2 backs.Lexicon owners swear they always watch all movies in the Logic 7 mode and it always sounds much better than any Dolby,ThX2 or Dts mode. Can that processor be that much better? Sorry for the long question But this is major purchase for me and I don't want to make a mistake. Thanks