why don't you ask the seller directly?
if you plug in a 220 Volts tube amp into 110 Volts outlets probably nothing will happen at all. It simply won't work as the internal voltage produced will be half of what is necessary to drive the tubes properly.
I'd recommend you to ask the seller about this voltage issue.
If he's a serious guy, he ought to give you an answer to this, otherwise I wouldn't buy anything.
The 220 Volts are probably the AC voltage they have in China and Hong Kong, in Europe we have 230 Volts and in the US it's 110 Volts. May be the producer of this amp can easily change the voltage by changing some internal parts.
I've seen this amp quite often on ebay.uk, the specs in the auction desription say: 110V/60Hz or 220-240V/50Hz.
You could also read the feedbach comments left on eBay to find out if the buyers were satisfied or not.
I hope that helps.