[terance]

  These are US made so you would probably have to call the company. It is the SL11A, here is the long list of power supplies that they make.
 
http://www.astroncorp.com/linear.shtml
 
This is who I called. Larry at Comart (800-777-2708) 

Is there a reason why this guy posts anytime someone mentions the iTube?
 
He never gives impressions, just advertises for Larry, just seems kind of fishy.
 
Anyways, The O2 and Aune T1's will both be side steps, not full on upgrades so I wouldn't bother with either of them.
 
 
Little dot ii+ might be a full upgrade, or definitely the Valhalla 2.
 
There is also a Canadian company who makes a really sweet $300 tube amp, but I have forgotten the name and can't find the link.
 
What source are you using?