Well, if 10 amps is the rated input current then the transformer VA rating would likely be 10 X 120 = 1200 VA. The actual short term amplifier output will be significantly greater at 1 ohm, limited to a large extent by the storage charge in the bus capacitor bank. I think these peak power figures at 1 ohm begin to get a little academic since there are few speakers with impedance dips to 1 ohm and, even then one would have to be driving the amp relatively hard to run into trouble. Also remember that if you are using the classical solid state amplifier, or any amplifier using global feedback, you may not obtain even the rated output power in areas where, and if, your speaker has an impedance peak (most do to some extent). Amplifier output power ratings are not so impressive at 15 or 20 ohms so manufacturers generally never publish this figure. Amplifier manufacturers such as Innersound have capitalized on this to some extent by offering high output current capability as well as high rail voltages. This allows the amplifier to maintain its rated output power over a wider spectrum of speaker types and their associated impedance demands.
Again, a lot of this is academic so don't read too much into it. The 4 or 8 ohm rating is still the most important.
