using a transformer to separate your gear power

We have used a isolation transformer for years. We use a standard line no current limiting conditioner for amps, pre. Isolation transformers for all digital. My HDTV for that matter. The differences with and without isolation transformers is staggering. We actually plug our isolation devices into our line conditioner for even greater improvement. The tonal qualities, soundstage, blacker blacks etc. is all improved using these devices. We do not use the balanced type so I'm not sure as to the safety issues mentioned above.

Isolation transformers should have a 20:1 ratio to work properly which is why we generally recommend them for digital components, televisions or pre's. As an example your IT should be rated at 8kVA to avoid transformer saturation. I may be in overkill mode but, better safe than losing dynamics.

The 20:1 ratio was the number used by the company that manufactures the ISO isolation device in order to prevent transformer saturation. This of course had a large margin of safety in it.

Radiate,
I would guess that your isolation transformer is not big enough for that much current draw. Note my previous thread about the ratio. Even if 20:1 is overkill I think your running into transformer saturation. We usually prefer these devices on digital and sometimes pre-amps and small televisions. Digital being the most important