Well, you actually sort of lose either way. If you don't upgrade, you'll be wondering how much better it would have sounded. If you do upgrade, you're out the cash.
A third alternative is to send the amp to me. This costs less than an upgrade and solves all those nagging problems with voices in your head talking about "CAST" and "dynamic envelopes" and "authority". I certainly wouldn't call you up and talk about that stuff. The amp would also sound better over here than at your house. Let me know.