TungSol 7581A Matched Quad
TungSol 7581A is a drop-in replacement for any 6L6 tube.
7581A can dissipate a whopping 35W, more power than any other current production 6L6. These tubes can be pushed as they have lots of headroom. If you wan to be able to push your amp when needed these are the rubes.
Price is for a closely matched quad (4 tubes).