When I first constructed my Paramounts I configured them with 300B and changed tubes to a couple of different brands, don't get me wrong everything sounded great. Then one day I was bored so I reconfigured to 2A3's, I had the tubes and did it. I won't go back to 300B's, I have since upgraded tubes from EH to JJ 2A3-40. I can't really explain but it sounds better, more detailed for lack of better word. It's easy to do, try it.
Make sure you have two extra HLMP 6000 led's