I'm assuming that you're referring to an ARC VT130se.
This can be tricky and expensive. I'm currently running Tung Sol 6550 power tubes, 8 of them, and they'll cost you at least 75 / tube. If you can find them. I also use 4 Siemen's 7308 tubes on the input section. These cost around 60 / tube. You'd need at least $840.
The problem that you would have is finding matched powere tubes. Also, note that this amp does not allow individual tube biasing. This can be a problem.
You can also use Svetlana KT-88's which seem to be quite available lately for a lot less - maybe 25 / tube.
Your safest bet is to send it to ARC to be retubed, but with shipping that will be expensive also - you'd need to call Accoustic Research. Unfortunatly you'd end up with Sovtec's.
I've also used GE 6550 and I like these 2nd best to the TungSol. You still may be able to get a matched quad from Jim McShane, look for the Citation website, for $200 a quad.
If you want to take this amp a step further, send it to Steve Huntley at Great Northern Sound. He'll replace the caps, and allow for a detachable power cord.
Hope I didn't frustrate you more!