You should take a look at PS-Audio website (www.psaudio.com)for their PowerPlants. In my system the PS 300 feeding the front end was the biggest improvment for the money!
I would suggest you look for a 1:1 transformer, with at least 3x the VA (Watt) rating of the equipment to be plugged into it. Preferably use separate trannies (similar specs) for digital & analogue devices.
BTW, there was a thread about this on AA very recently... (I didn't find it when I looked just now, sorry)