$1000 used amp. What can I buy?

Threshold - (Cas 2,400A,SA3,S150,S200,) Forte 4a, Muse 100 or 160 , Pass Labs Aleph - (3 or 30 or 5),Sumo - (The 5 or The Nine or Andromeda,)Classe DR Series any of them,my favorite here is the DR 2 and DR 8. Bryston 3B ST or 4BST.

Might want to consider another preamp, from the same manufacturers as listed above. With most of the amps listed above you may find that a sub woofer is not needed,unless your speakers only go down to 45Hz.

Give the McCormack amps with revisions a try. They are rarely sold for very good reasons, one of which is they sound superb. You may also look into some of the digital amps like PS Audio's HCA-2, quiet, runs very cool & load invarient.

I definitely like your suggestions.

WIth every system I have owned it has benefited from splitting the low frequencies from the main speakers. That might not be the case with large speakers that have dedicated cabinets for the low end drivers, but those are usually recommended to be biamped as well. But we are now talking much more money than most of us can spend. The midrange seems to open up with the bass being ran through a separate driver and amp. Getting rid of the low frequency caused distortion of the woofer allows lower distortion in the midrange. Also this lowers the power requirements to drive the main speakers. The down side is that you are adding another part(external crossover) that can degrade the signal and parts must be of high quality.

Musical Fidelity A3, A3.2. Dual mono design, very nice