SET amp comparable to First Watt SIT 1?

Border Patrol makes a very good 300b SET (as well as 300b PP) amp. Not cheap, but they often have pre-owned units for sale. www.borderpatrol.net. Gary Dewes is very knowledgeable. If you go this route, I strongly recommend Takatsuki 300b tubes.

I would try your current amp first and see how you like it. You really can't trust someone else's opinion on this type of thing. If you end up looking for a new amp, Shindo is a very good choice. I happen to know the importer for many years and have a lot of confidence in him and the products. When you buy expensive, specialized components like this, made in a different country, its always good to deal with reputable people that will stand behind the product. I have expensive tube amps myself, and sometimes things go wrong and you need to have them serviced. 

Tmare, there was a long thread on Audiogon a few years ago about First Watt vs SET amplifiers. Many good comments based on actual listening to both. As expected there was no consensus, some chose F.W. S.I.T.and others said their SET was preferable after comparison . Just too many variables involved to arrive at an absolute winner. You’re right about the many choices of 300b SETs available and there is a hierarchy. You don’t have to use the ultra expensive W.E. tubes to get superb sound quality Takatsuki and EML XLS are excellent choices. The Elrog 300b is excellent however only reliable in certain amplifiers, so they aren’t a universal choice.

With your price range you can get truly terrific SET amplifiers with top tier quality output transformers and power supplies. I believe the S.I.T. or a high quality SET can make you happy long term. Take some time to do some research. Gary recommend Border Patrol, other good contenders Coincident Frankenstein MK II, Triode Corp of Japan TRX series, Audion, Airtight, Audio Note, Wavelength, there are definitely good choices available. In your price range you can get truly fine 845 SET amplifiers if interested. 
Charles