I agree on building your own PC. I built one using a cheapie case and power supply and it was pretty quiet. So I ordered another case and power supply, same catalog number from the same supplier, and what came was a bit different. The power supply was the worst broad-band noise generator I have ever met, even when the computer was turned off. I've been told that Antec makes good power supplies and boxes.
On the other problem, high noise on CB and 10 meters, I've found that a battery-operated portable shortwave receiver is a great tool. I had a lot of trouble at first with power line noise. The power company was cooperative but not very skilled in finding it. I could walk around with the battery receiver and find the noise hot spots and then they could find the faulty line hardware. I read somewhere that your house is a high noise zone, and if you get about 15 feet away things get much quieter. I haven't yet got around to trying that with the portable SW receiver. I'm told that even wall-wart power supplies these days generate RF noise. Touch lamps are known to be a bad source of noise. One of my friends says to turn off Everything in the house, unplug all the wall warts, and see what kind of noise you have, and then put things back on one-by-one.
