You're right on target! The Tympani 4s sound awesome biamped. Go for the monoblocks (all your choices sound great, the Tympanis were often demoed by Magnepan with that era of Levinson amps so those might be my first choice. In theory you can have tubes on the highs and solid state on the lows, but you may find that the sound is not cut from the same clothe this way and even with an electronic crossover, may not blend very well. I think it would be better to use the same types of amps throughout the sound spectrum. I know this from my experiences in biamping both Magnepans, (Tympani 4s, MG-IIIs, MG 3.6 and Revel Salons.
Hope this helps,
Steven
Hope this helps,
Steven