Look on E-Bay for 'tube amp' and you'll find a number of items in your price range. Most are Chinese imports, but my limited experience with these types of products is that most sound pretty good as long as they are not pushed too hard.
Inexpensive tube amp
I'm looking for an inexpensive but yet decent quality tube amp to pair with my new Zu Omen bookshelf speakers. I've noticed that there are a lot of integrated amps out there, but I would rather and Stand alone amp to pair with my existing Preamp. The preamp is a modified Acurus unit from back in the day. However if I cannot find an inexpensive amp an integrated unit might be okay. My budget will be between 300 and $400 new or used. The source will be an old pioneer turntable. Nothing special just an inexpensive analog front end to listen to music in my small room.