NOS KT 88s or GE 6550s

Sunnyboy, I have heard both the GE 6550's and the GL KT88's. IMO, the GE's are some of the very best tubes ever made. If you like midrange magic and the ability to drop down in the bass dept, then you will LOVE these. The GL KT88's are almost veiled in comparison. The SED 6550's are very very good and are a fairly close second to the GE's in the 6550 range. Only problem is the GE's are usually very hard to find in decent condition.
I say go with the GE's if your amp can use them.

Pradeep, I haven't heard the NOS JAN 6550A...were these GE's as well and just Joint Army/Navy or ?? I do own a matched quad set of GE 6550's that are like new, and once my SED 6550 C's give up the ghost will replace them with the GE's. You have to be VERY careful that the GE's you will be receiving will still be good. I have heard several horror stories about supposed NOS GE's going up in smoke. I had this happen on my amp when I first acquired it, however, I knew that the tubes were very old and it was a matter of time before ..poof. Happened almost immediately after I acquired the amp...luckily no other damage except to the tube itself.

Hifigeek1, perhaps if you could listen to a good amp using the GE6550's you would see what the fascination is all about.

Hifigeek1, what newer versions are you talking about? The GE 6550 tubes that I have used and heard were all very good sounding and quite reliable. If you are talking about another brand, well that's a different situation.

Hifigeek1, I trust the Richardson 6550's weren't GE branded, or??