Need suggestion on VTL TL-5.5 tubes

I've been using TL-5.5 preamp and I like it a lot. Recently I'm trying a different amp, which has much higher gain than the current amp, and noticed I'm hearing a lot of background noise now. The source of the background noise turned out to be my preamp. With preamp off, or out of the chain, there is no noise. My speakers are 93dB efficient, and the new amp has about 25dB of gain. The background noise is loud enough it's heard/felt at the listening seat at 8 ft away. It's clearly heard about 1 ft away from the speakers.

I really like my preamp and I'd like to keep it if possible, but I must eliminate the noise. I'm not sure if the noise is due to aging tube or other part of the component, or simply noisier nature of tube gear. My questions are:

Are there other TL-5.5 users with sensitive speakers that can comment on how much noise they are hearing? It's also dependent on the gain of the amp, as with my previous amp with 15dB of gain I don't hear ANY noise even when ear pressed against the tweeter, maybe except for slight hint of hiss.

Should I try new set of tubes? If so, any recommendation on 12AX7 and 12AT7 with very low noise floor?

Third question, somewhat tangential to the issue is the need to reduce overall gain. The useful range of volume knob is now from 0 to 10 o'clock. It needs fine adjustment by hand and it's not feasible to use remote control any more. Is it possible to reduce the gain on the preamp with a different set of tubes?