Tube Recommendation for Anthem Integrated 2

Amperex 7308 is one of the better choices.
also Sovtek 6922 sound better than most 6DJ8

You might try and find Brimar 6922. Anthem uses these in their upgrades. I installed one in my Anthem CD-1 CD player.
Should give you a warmer sound. Good for jazz.

I used to have the Anthem Pre2L preamp. I tried Siemans 7308's per Kevin Deal's recommendation. I then tried Amperex 7308's due to alot of recomendations here and over at the audioasylum. I prefered the Siemans over the Amperex for the Pre2L. The Siemans gave me exactly what you're looking for -- smoother sound and tighter bass. The Amperex also sounded good but the vocals were more forward, a little more energy in the highs, and the bass was a little more rounded and relaxed. I'm sure others may prefer the Amperex, depending on their system, room acoustics and personal tastes. The Siemans are noted for tight bass. I now use the Sonic Frontiers Line 2 with 6 Siemans 7308's.