There are a couple of great sites for current production tube "sound" evaluation.
The tube depot here in Memphis TN has some great information on pre and power tubes and a great bunch of folks to do business with too.
Also the Tube Store in CA has a plethora, I have waited a long time to get that in a post, of info on current production tubes as well.
Both sites have some great articles posted as well as some links to some other cool sites. Just like dude said. Read up, think about what you are looking for then try them out.
When I was running EL34's I preferred Tung Sol or Mullard RI's. EL84's EH's were my favorite. I found I wasn't a fan of 84's though. Too bright but the EH 84's were more 34 like as far as darkness goes. Still a little bright but not as bright as the others I had used.
I am using two Marshall Mosfet Lead 100's (sacrilege I know) but I like the reliability and the fact that you can pick them up fairly cheap! I run the RM4 through the effects loop on one and use the other one input to output into my stereo Randall cab. A little bit of chorus to get some distance and then mic eliminators out to the recorder and it is so 3D sounding!