this is not a question of "bridging" (which involves using two or more stereo amps as monoblocs) but one of bi- tri- or quad-amping. first, you'll need a preamp, or direct source with volume control, that has 2 pair of outputs or more, fairly unusual unless you use single-ended and balanced simultaneously (not recommended). second, you'll need a pair (presumed) of speakers that are bi- or tri-ampable (your infinity bass towers do NOT appear to be bi-ampable). then it's just a matter of impedence matching and purchasing a sufficient number of (matching, i should hope) speaker cables.
