Tube recommendation for Audio Research LS-2b?

I have an LS2B-MKII and have compared the stock Sovtek 6922 with an Amperex 7803 (PQ/Orange). The Amperex was much more detailed but added a slight sibilance. I'm not sure if the tube was the issue or whether the preamp needed a bias adjustment. (the seller said the tube was NOS and tested well).

The 7308 is the top of the line tube in that category. The Amperex is an excellent tube. Very low noise. Provided it is a legit Amperex. It should have a number etched in the tube I believe.

Yes a large '253' is etched vertically near the top. The orange labeling is easily scratched off, however.