I'm using 4 mono's. I'm using different amps for the top and bottom, based on the characteristics of the amp and the sound I'm trying to acheive. I use Levinson Reference 20.0 on top, and Krell KMA 160 on bottom. The Levinson's are smooth, well defined, and excellent image presentation. The Krell's provide the bass authority needed and have a high damping factor, which improves the bass timber. It's an active cross-over system. I wouldn't recommend different amps without an active cross-over.
The Odyssey is relatively new, but the reviews are amazing, and I agree, at that price it makes bi-amping very affordable. The benefits greatly depend on the speaker. I'm using Martin Logan Monoligths. The combined demand of the low impedance from the panel and the high output demands of the woofer make bi-amping a huge benefit by separating these demands to separate amplifiers. Other speakers may not have as much benefit from bi-amping.
The Odyssey is relatively new, but the reviews are amazing, and I agree, at that price it makes bi-amping very affordable. The benefits greatly depend on the speaker. I'm using Martin Logan Monoligths. The combined demand of the low impedance from the panel and the high output demands of the woofer make bi-amping a huge benefit by separating these demands to separate amplifiers. Other speakers may not have as much benefit from bi-amping.