While the various philosophies of use applied to interconnects and speaker cable have been bantered about the campfire here quite a bit, I had a similar question that I asked of Outlaw before I made my first Outlaw equipment purchase. I asked which they thought was better, mono amps at near each speaker (long interconnects, short speaker cable) or all amplification near the pre/pro (short interconnects, long speaker cable). Their answer was the latter. I think the reasoning is that electromagnetic interference, if present, would work its evil more easily on long interconnects than on long speaker cables. This would seem to bode well with regard to your intention of keeping most of the electronics in the closet intended for them.

Extra thought: will heat build up in the closet?

As far as speaker cable goes, many people are trying many things, my personal philosophy runs toward the technically verifiable. As a result, I would go for cable that is permissible in-wall, if you are running cable in-wall, and which will have a maximum round-trip resistance of 5% of the loudspeaker impedance, less than half that if such cable would be reasonable. Assuming 6-ohm nominal speakers, 5% resistance would be 0.3 ohms. Going 50 ft. out and back with 14-gauge copper yields 0.297 ohms, 12-gauge 0.187 ohms and 10-gauge 0.118 ohms. Less than 50 ft. would mean even fewer ohms. Speakers with higher ohm ratings could use lighter gauge wire, 4-ohm speakers would require slightly lower gauge wire. Perhaps, with the equipment at the rear of your room, you would use the heavier gauge for your fronts and center, lighter gauge for your surrounds/rear. Because the lighter gauge would run a shorter distance, the nearby speakers would see no more cable resistance than the more distant speakers. You could also use heavy not-so-flexible wiring inside the walls and more flexible and attractive cable between walls and equipment or speakers.

If you would like to read more on speaker cable ‘honesty,’ you might try these sites:

http://www.roger-russell.com/wire/wire.htm#gordongow

http://www.epanorama.net/documents/wiring/wire_resistance.html - discusses skin effect near the end of the page.

http://sound.westhost.com/cables.htm