Upgrading 2 channel stereo.

Sorry if this question has been beaten like a dead horse but here I go.....
I recently upgraded my main L&R speakers to B&W 805's. I love 'em but now I gotta upgrade my electronics.(mainly for 2 channel stereo. I am currently satisfied with my HT performance.) I am currently using a Marantz AV550 pre amp and MM9000 5 X 150 amp with a Marantz CD67SE and a Velodyne HGS12 sub. My speakers sound real nice but I realize they could sound waaaaay better. My original idea (little $$)was to get a cheap 2 channel amp (NAD, Adcom) to drive my rears and then bi-amp the 805's with 4 of the 5 channels in the MM9000.
Then a sales guy told me I'd be better off buying a fatory refurbished NADT761(they had quality issues but supposedly the refurbished ones ore OK) for < $600 and using that for a pre-amp and only using 2 of those channels for the rear and then using my MM9000 to bi-amp.
Then there's always the idea to use the pre L & R outs of my existing AV550 into a quality integrated (krell 300iL, creek, Musical Fidelity, etc...) but then I loose my sub with 2 channel stereo.
Then theres the idea to upgrade my AV pre amp to something more musical. (B&K Ref 30 ??) But then would my MM9000 be sufficient ??
I guess my budget is <$2500. (My wife's gonna kill me !!)
Any input would be appreciated.
I had both a Marantz AV550 and a Marantz SR880 receiver along with a Marantz CC65 Cd player. Let's just say I miss the 550 but not the 880 nor the cc65. This is why: Marantz features are great and easy to use. Marantz amplification is only mediocre sounding (flat)in comparison to other amps that are just a little more money (newer adcom, nad, sony es, rotel...). I honestly think you will be quite dissapointed with the older NAD amp. Also, marantz single bit cd players work great but don't sound nearly as good as similar cds from denon and rotel.

My suggestion: Keep the 550 for now, spend your money on some very nice amplification and see how that goes. The 550 with a nice adcom or rotel amp should blow away the NAD. You've got beautiful sounding speakers, let them sing!
If it were me, I would run the CD67 directly into a nice integrated that had pre outs to add a sub. You could run the AV550 into the integrated if you have a tuner and DVD and CD all hooked up to it. Otherwise, I would just run your source into the integrated. I can almost guarantee you are going to get better sound with one of the integrateds you listed than if you try to biamp with marantz. You have a speaker with a ton of potential. The Creek and the Musical Fidelity are both good. You have tons of options as far as integrateds go in this area. Classe CAP 151, YBA Passion, Pathos makes one called the Classic One for less than the Creek 5350SE. That would be the direction I would go if you are looking for something that will give you great sound and don't want to worry about upgrading for a while.
Thanks for the input Elevick and S7horton.
One other problem that I can forsee is how do maintain a
HT sub off the (single) sub out on the AV550 and have the same sub hooked up to (left & right) pre outs on a nice integrated ? I can imagine some sort of switch to toggle between the two.
Would I benefit at all from just updating the L & R Amp(krell KSA100, McCormack DNA125, Belles 150A Hot Rod, Citation 1.5)and keeping my AV550 ?