Polyglot,
Congrats on the CT5! It's a marvelous preamp. I bet you got an amazing deal now that the ET 5 is out.
I decided to stick with CJ's supplied Sovtek tubes because the majority of posts I've read around the forums and boards indicate the expensive alternatives for the CT5 don't yield much bang for the buck. I'd love to hear if you have a different experience. How do you like the unit so far?
I *do* have one tip: Try a Hifi Tuning Supreme fuse in place of the stock fuse supplied by CJ. The fuse is accessible from the rear and relatively easy to swap out. Let the new fuse burn in for about 50 hours and then reverse the direction. You'll hear a difference and then you can know which direction you prefer. The fuse runs around $55 and is worth every penny, IMHO. I also use a Shunyata Python CX power cord (*far* better soundstage and transparency than the stock cord).