Can anyone help me to decide which pre-amp is better ?

It really depends on how much of that midrange bloom you are looking for - all the pre's mentioned are great and it is more a decision of taste than quality and accuracy! The AudioNote M2 has more bloom than any of the pre's mentioned but probably lacks in many of the other area's. The Lamm and First Sound are options along with Blue Circle, they have a new ballanced pre that sounds great!

The blue circle 21 and Rogue are about the same price new and used and both supposedly sound great. I have 10t's and unless you are going to get some big power tube amps like VTL 450's, a fast powerful solid state amp is needed for 10t;s. I am using a Spectron and it is 500 watts channel into 4 ohms. It runs the 10t's well. You might want to try mono block bel canto evo's. Have fun, sounds like you are on your way. I use a VTL pre 1 tube preamp /and a passive unit also. Enjoy the music.

Jeff -

Of the preamps you mention, I would go with the CAT. When I was shopping for the best preamp for my demo system, three brands stood out to me: CAT, Lamm, and Thor. I chose to become a Thor dealer, but think highly of the other two.

Kora is well worth considering. Lots of sound for the money.

One thing to consider for HT is that the pre-amp have a bi-pass or an input that has goes straight through with no gain for your main channels. In solid state there are quite a lot of pre amps that do this, but in tubes it's a bit rarer. If I'm not mistaken I believe the CAT does have this feature (it's also a great pre-amp), I'm not sure about the others. Of course, if you find a pre-amp you love that doesn't have this you can always have a particular volume setting that accomplishes this--but I've had a system set up this way and it didn't bother me at first, but after a while it got old setting the volume all the time.