I'll add my vote for monoblocks. I have mine directly behind the speakers.
I have all my equipment on the side of the room, because I've found having open space between the speakers helps a lot with the imaging. I run long balanced interconnects from the preamp to the monoblocks. Good quality balanced interconnects are less expensive (and much easier to hide) than good quality speaker cables, and I think have much less deleterious effect on the sound quality than long speaker cables.
I'm running 8 meter interconnects. In the past, I did a fair amount of testing between shorter balanced cables and longer lengths and (as long as I was using a device with a low output impedance) I could not tell the difference between short (1M) and long (tested up to 10m) lengths.
But I agree with Mike and Early B that the primary benefit is completely separating the circuitry including power supplies. Besides eliminating any channel-to-channel interaction in the power supply, it also eliminates a major cause of ground loops caused by having two separate ground connections between the amp and preamp (more of an issue with single-ended connections than balanced connections).