ok so on the Lenovo HTPC the cpu utilization before running plex was close to 0. while using the plex media server to watch a movie, the cpu utilization was 100% and the movie would buffer every 5 seconds. using plex media player, cpu utilization was 100%, there was no buffering but the video was choppy beyond use. I installed windows updates, disabled some startup programs. I ran the same tests on my own machine with the i7-2600k and the cpu utilization while watching a movie using the plex media server was 100%. while playing it with the plex media player, it was less than 100%. the reason for the difference is that when using plex media server (through the browser), there is transcoding going on, but while using the plex media player, its using direct play.
Family Room: Onkyo TX-NR 646 AVR, Polk Audio RtiA3 fronts, Polk Audio CSiA4 center, BIC America F12 sub, Polk Audio RC-65i rears
Basement: Denon AVR-X3400 AVR, Klipsch RP280f fronts, RP450c center, SVS PB-2000 sub, Polk Audio RC-85i rears & surrounds