Any way to reduce pre-amp noise floor?

The 6922 is part of the 6DJ8 family along with the 7308. The 6DJ8 is at the low end, the 6922 is in the middle and the 7308 is the big brother. These tubes vary in their electrical characteristics but that stuff is over my head.

Most people consider them interchangeable and opinions vary on which sounds best in a given preamp, as usual. I would stick with what c-j told you. They probably have a reason for it.

That's the problem with tubes. They can make noise, die prematurely, etc. That's why the engineers came up with transistors. Any tube can cause trouble at any point in its life, but if you buy good tubes it shouldn't be a common problem. It's the price you pay for that nice tube sound.

There are plenty of 6922s to try though. If you want to try vintage tubes, the Amperex, made in Holland or the USA, is a popular choice. If you want current production, check with Jim McShane. Tell him what kind of change you would like to make to the sound of your preamp and see if he can recommend something that would work for you.

Whether you go vintage or current production buy from a reputable dealer. It will save you a lot of time and money. The good dealers are more expensive but their knowledge of tubes is worth the extra they charge. You have to learn quite a bit about tubes before you start buying them off Ebay or you'll end up wasting a lot of money.

There are good sellers here on Audiogon too. I can't vouch for anyone in particular, maybe someone else can.

The good dealers will be willing to answer your questions and make recommendations. Don't be afraid to tell them you're not knowledgeable about tubes. If you're not sure after talking to someone, just tell them you need to think it over. They are used to talking to people who know nothing about tubes. It's in their interest to turn you into a tubeaholic and repeat customer.