Balanced lines solve hum problems?

I'm having a real tough time killing a low level hum coming out of my Martin Logan Quest speakers. The set up consists of an Oracle Delphi IV and YBA CD Integre source components, fed into a Audio Research SP9 Mk II Pre-amp. 25' single ended interconnect to a pair of bridged Classe Audio DR-8 amplifiers. From there, (8) 8' runs of speaker wire to the Quests complete the system. I've put in hospital grade plugs, and grounded the amps to a cold water pipe, a little better, but still a hum exists. One of the guys I work with feels I have a 100hz hum, likely coming from a motor (i.e. fridge). He has suggested I change from single ended to balanced lines, and the problem ought to go away. To do so, means inserting a DI box in the signal path to convert single ended to balanced signals, via an isolated transformer, I'm not in favour of this approach. Another option is to sell my Audio Research pre-amplifier I love (great phono section) and find another pre-amp with balanced outputs, more than likely a line stage pre-amp that requires a seperate phono stage. Much money and hassle, is this the only way to solve this problem? Opinions are most welcome, thanks, Jeff