I assume that you know that the 5881 is the commercial grade tube that replaces the 6L6.
I strongly recommend that you get 5881 tubes if you can. They are an exact replacement, but with higher ratings and usually will sound better and last longer. The Sovtek are probably the best you can get.
The Sovtek 5881WXT is available in matched pairs from Musician's Friend. They are $40 per pair. They are pretested and individually matched.
Originally Posted by jdoostil
I am running a Mcintosh MC240, and its time to replace my 6L6 power tubes. Since I have owned this magnificent piece of art, this will only be the 2nd time Ive had to replace the tubes. I have Bugera tubes now. I have been happy with them, but Ive never had anything to compare them to. There is a HUGE price difference with 6L6s. Any advice or help is appreciated!