levinson amps/preamps have improved greatly over the years, and while the 23.5 is still a good amp (with tons of clean power), it doesn't throw much of a soundstage (i know, i owned one).
the 331/332/333 series got bested by the pass aleph 3 in an embarassing comparison in stereophile (which you can now get for $950 on audiogon). but if you move up to the 334/335 or the new 400 series, you will get a big jump in transparency and soundstaging. i'm partial to the 334 due to the more robust design and reportedly better bass over the newest amps, but that may be more opinion than fact.
i also had B&W matrix 801's years ago, and they were/are very resolving speakers, so the nautilus line is probably even more so. the differences noted above will be very evident on N-802's. as for home theatre, you should consult with a dealer for less expensive brands if you're going to add alot of other speakers/amps/HT processors. but for faithful reproduction of 2 channel music, levinson ain't bad. (rowland's okay too...)