I recently bought a LSA VT-70 tube amp for $1,300. It is a great buy and has received a number of very good reviews in several audio publications. Yeah, that's not a LSA Warp, but Underwood's LSA brand is solid gear at good prices.
Is my amp perfect? No, but then nothing is. Does it get me where I want to go with a tube amp? Yes. I think it would take me several times the price of the VT-70 to get a substantial improvement.
What's an acceptable performance and price vary widely between individuals. I'm very happy with the VT-70. I know others who would never spend $1,300 on an amp, and still others who would turn their nose up at this. So this is a decision you need to make for yourself.
Concerning trials, the Underwood web site is silent on this issue. However, one reviewer said Underwood allows returns for up to 30 days, but with a 15% restocking fee. If this is a concern, I'd suggest you give Wally a call and hear their terms and conditions straight from him. He is not hard to get ahold of and loves to chat.