Hooking up two Topaz Isolation trans. in series?

In fact, with two transformers in series, you would get slightley less power (1-2%), due to the iron losses of the second transformer. There is no free lunch in Mother Nature.
You will get more isolation, but ALL transformers add slight distortions, so you may be trading isolation for unwanted AC harmonics.
I have measured increased 5th, 7th and 9th harmonic distortion of the AC waveform out of a Felicia DIY project (two isolation transformers in series, with filtering caps in-between).
Google Felicia...I read all the gushing comments and wasted U$ 200 on two custom 500W iso transformers. I heard distortion in the treble, it was confirmed by borrowing a friend's AC harmonic distortion analyser.
Bummer...my Cd player sounds much better connected directly to the wall receptacle.

In order to implement iso transformers correctly and get rid of ground loop issues, I suggest that you read the following paper:
http://www.exactpower.com/assets/pdfs/theTRUTH.pdf

Good luck

I found separate iso transformers gave best results-clearly audible. Amps should be isolated as they create significant noise, digital is obvious, and of course you want to isolate the very sensitive preamp from ac noise.

KVA rating is the peak voltage x peak amp x 1000 rating for the transformer or the peak wattage rating. RMS (root mean square)is wattage rating which is 0.707 of peak voltage. All engineers will size for actual plus fudge factor. Normal fudge factor is 40% above max expected for safety/performance margin. Large margin increases cost and may not protect against certain failures of down stream units.

To get more iso watts add more transformers and move loads to each separate transformer. The sum of the transformers will add watts without connecting secondaries and offer superior performance and safety. Loads will be isolated from line issues as well as each other.