As far as vertical biamping vs dual bridged monoblock, depends on the bias of the amps and impedance of speakers. Class A amps, in order to stay in class A, should drive above 4 ohms and bridging only increases A/B power, albeit by a factor of 4 (for most SS). Essentially, bridging is a lot like cutting the impedance of the speakers by half. If the speakers are already low impedance, they can be a difficult load. The upside of bridging is sheer power, the ability to use shorter speaker cables and monoblock separation (as rumoured). The upside of vertical biamping is easier loading and something called transconductance, which is the reactance of the woofers/x-overs across the entire bandwidth. Which is better for you is up to experimentation. The Macs are a sturdy design but the IRS line is notoroius for being tough to drive. When the Kappa 9's were released, many highly regarded amps of their day got their smoke let out.
Infinity was tight-lipped even before Harmon bought them and very little specific info was published. The Infinity Classics website closed down, unfortunately.
