I'm not into surround, striktly a 2 channel man, but as far as connections go the principles are the same. If you want the best possible connection on a long or short run, you site the monoblock near the speaker and connect the P9 to the pre amp with XLR, rather than RCA, then use the shortest possible speaker cable.
The ideal speaker cable length is zero; none at all. Speaker cables have no really effective shielding and deleterious cable effects increase with length. XLR cables, between balanced DEVICES, prevent most noise via common mode cancelation. This only works well with properly implemented cable designs (and most are nowdays), and balanced devices, not when using RCA to XLR adaptors with non balanced devices nor with a balanced device at one end only. So to get the benefit of this, you need a pre amp with balanced design and XLR out. In this type of use, the benefit of XLR is real and very noticeable.
Next best is same layout with long RCA. However, RCA cabling between devices (balanced or not) relies on cable shielding, not common mode noise cancelation, so the quality of the shielding, and the earthing of the shield are critical. Floating shield cables (such as is common in xlr and short run silver RCA like Chord) should not be used for long RCA cable runs. The shield earthing end needs to be identifiable and connected to the source (pre amp) end; most good cables feature this nowdays. Tight bends in a long run of shielded RCA should be avoided too.
If it were me, I'd site the amps very close to their respective speakers and use long XLR cable runs, with speaker cable kept down to a few inches or a couple of feet (and at this distance, the audible difference between expensive and cheap speaker cable is almost nil). If my pre-amp didn't offer balanced designed with XLR out, I'd do the same with RCA. It's worth noting that an XLR cable between a pair of non balanced deviced or between a balanced and a non-balanced, is worse than an RCA; both ends need to balance to make it work or else it's just a noise aireal without the benefits of the earthed RCA shielding.
Hope that is what you were wanting to know.
