I'm looking to make my first foray into the world of tube amps and was hoping someone could give me some much needed advice on a good beginner amp that costs no more than 5 (ok maybe 6) hundred, second hand.

I am currently running the following:

CA CXA60 amp
CA CXC Disc Transport
Monitor Audio Bronze 6 Speakers

I listen to blues, soul, country. Artists like Jackson Browne, Ry Cooder and Little village. I like the thick, warm, choral quality of tubes - to my ears at least.

Thanks in advance.