Tube favorites for Modwright LS100?

Try the new production Tung-Sol 6SN7-GTB at about $20 a tube
They are really excellent. I am using them in ASL Hurricanes

You could also try some Sylvania 6sn7 "Bad Boys" or some of the early 1950's Russian (Sovtek) 6sn7 with the metal base.

I agree that the new production Tung-Sol's are very nice.

Also check here for more info:

http://www.audiocircle.com/index.php?board=14.0

For the 6SN7 I'd give the Shuguang CV181 Black Treasure tube a shot. These take a bit of break in time and in my experience will fluctuate widely in performance in the first few hundred hours, but the stable performance after that will be worth the patience. I do not have experience in that preamp though. You might be able to find a used low-hours pair for $150 or so. There are some NOS Russian variants that are quite good too, but their prices seem to be going up dramatically lately...I think the pair I have that I really liked is a metal-base 6H8C with round-hole plates. The plastic base version of the same tube is also pretty good and cheaper. As far as the rectifier tube, a sleeper tube in that family is the GE copperplate. You might also try a 5U4G, like an NOS Tung Sol in there as I think you can use that tube family as well.