What you are contemplating is the bi-amping approach called "passive bi-amping" (leaving the speaker's internal crossovers intact and using the high and low frequency binding posts to connect two amp channels to the single speaker). You would only need a pair of Y-splitters and some extra speaker cable to connect the four amp channels to the two speakers. It can effectively increase the overall power available to the speaker, which can be helpful at higher listening volumes but may not provide much noticeable improvement at lower volumes. I think the 7125 would be a good fit. There may be some other Polk RTi10 owners around here who could offer some more first-hand feedback.