Balanced Power

I believe that Exactpower makes a unit that does this, for around $1k. You can't get there just by simple wiring changes to your existing house wiring; as stated above, you need an isolation transformer and they are not cheap.

Stehno, there are two ways to get there: One, take your house's 240v supply and run it through a stepdown transformer wound 2:1 (240v to 120v). Or two, just pass one of the 120's through an isolation transformer (wound 1:1 with a center tap for ground). The end result is the same. One approach may be quieter than the other depending on the type and magnitude of noise on your AC lines, but it would be hard to say which would be better without trying both.

To try to clear up the confusion here:
Normal house service is wired 240v balanced, meaning two 120v legs in opposite phase plus a neutral wire. The two 120v legs alternate in the panel from one breaker slot to the next in a vertical direction, on both sides of the panel. Any double circuit breaker (just like your clothes dryer uses) will give you 240v balanced. On the other hand, all 120v is taken from one or the other 120v legs plus the neutral wire. Half of your house is wired from one 120v leg, and half from the other, in a random fashion determined by the guy who wired up the panel. There is no way on heaven or earth to get balanced 120v (meaning +/- 60v with neutral) out of this setup by simple wiring changes. You must use a transformer. I hope this helps.