Ramoneo14,
Congratulations on acquiring your new horn speakers. Your speakers may be efficient and sensitive enough to be adequately driven with a 45 or 2A3 SET amplifier, how sensitive is the speaker?
I’m more familiar with 300b SET amplifiers and fortunately for you there are many High quality choices available. Gwalt mentioned the necessity of a "stiff"power supply and he’s correct. I would add that output transformer quality is a crucial factor. The Border Patrol amplifiers he cited and my Coincident Frankenstein MK II SET are two examples of very high quality 300b amplifiers, there are certainly other fine choices as well.
Do you have a specific budget? Be careful with lower priced SETs, there are good value amps to find as long as corners aren’t cut in regard to power supply and transformer quality. If you exercise some patience and do some reading and research you’ll find a very good match for your speakers. You're on the right pathway, a high quality 300b SET will provide you with superb music reproduction.
Good luck,
Charles,