Best amps for new B&W Nautilus 800's


I just purchased the new B&W Nautilus 800's. These babies will play a dual role in my home theater and for music listening -- more music than theater use. I have listened to Mark Levinson 336, Classe CAM350, Classe 401, and Krell 300c. Am also interested in Krell 350Mc's and 600c. These amps range quite a bit in price, and I'm willing to spend money -- but I want to spend SMART money. My pre-amp/processor is the new Theta Casablanca II with Extreme DACs. I haven't selected a new DVD or CD transport yet. I like strong bass and want to control the speakers with authority. Please help me select best amp.
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A friend who operates a retail audio store recently traveled to England for a tour of the B&W facility. During listening sessions he observed that Mark Levinson amps and preamps were in use.
Taking this discussion to modern times (only 14 years later), utilizing the 802D3 speaker. 
Mid you had a choice to use TWO stereo 250 WPC amps to vertical bi amp, or one PAIR of monos at 400 watts each, which would folks suspect would be better?
i realize you would need two pairs of speaker cables to biamp, and only one pair (using supplied jumpers), or one pair of bi wire ready wires w the monos.