Steve,
Great stuff... I have been evolving a system sorta like yours. I have three recording MC machines and a WHS. I just added a Linksys DMA-2100, which works great in the bedroom and after reading your write-up, have added the commercial skip add-in. I would go all extender, as you have, if I can figure out how to deal with the need for more than 2 tuners (with cable boxes) and therefore how to integrate two closet MC servers instead of the one you have.
My 'main' HTPC, in the front room, is a home built Vista Premium machine with a 3.6Gh P4 chip. I have used it for 3 years and it has worked great. Both tuners have MPEG2 hardware encoding and I have a AGP ATI X1600 Pro graphics card. The CPU usually would operate at 20-30% most of the time while watching and recording TV.
Since I installed the extender and commercial skip add-in, it has been ramping up the fan speed, and noise, multiple times a day - which is very irritating. The only time it would ever do that before is when it was running its nightly Norton scan. I checked and the CPU is running at full capacity with mostly the extender and commercial skip processes. The commercial skip is taking over 1/3 of the CPU. Does this make sense to you and is this just the way it is - new CPU time??
Thanks, in advance, for your whisdom.