Stehno makes a key point in that dedicated lines will not clean up the AC from outside your home, and unless you have a dedicated ground on that dedicated circuit you will still get feedback from other appliances in the house. I have 3 dedicated lines (10 guage, 20 amp, power ports) but grounding those on existing ground did nothing to alleviate EMI from other appliances. Some use a seperate (dedicated) ground for their dedicated lines but I've heard this can be potentially hazardous because of potential between the 2 grounds.
Even after the dedicated lines I heard variable quality from system so I went to power condtioning as well. Originally PS300 on sources only, now I have BPT 3.5 Sig. on everything. No variability anymore, noise floor has dropped considerably, stable image, etc. If you have dirty AC this is the way to go.