Was doing some looking on ebay for vintage gear (I'm an addict), and this puppy caught my eye;

http://cgi.ebay.com/Fisher-500-C-Tub...QQcmdZViewItem

The really special thing about this one is that it's been upgraded for "modern" usage. The big plus in my eyes is that it's had cathode resistors added to the output tubes. With this if you blow an output tube your output transformers are protected. That right there can save you a lot of drama if you get a bit carried away, as I've been know to do!