Can I use two preamps?

Yes,No problem,very safe for pre-amp,but not operating a tube amp with only one channel,Enjoy

Thanks for the advice all, and I think I will try a 3dB attenuator first like you said Stanwal to see if that works. This is obviously cheaper than getting two, and it might just work. Rwwear, unfortunately, my M60s are not balanced, so the XLRs are not possible, but that does sound like an idea, and now I know how to if I ever end up w/balanced amps.

If you want to pursue the two preamp mode, I don't think it will be problematic. But the best way to do it it my opinion would be to invert the outputs on both and make them a truly balanced configuration. To do this you would simply need to make a set of "Y" cables with RCAs on one end and a female XLR on the other. Combine the two grounds on pin one of the XLR and on pin two one of the positives and pin three the other positive. This is of course only going to work if you have a balanced amp. Sounds like a fun project.

If you're set on QS then Stanwal has given you the best advice. A tad on the high side but these are excellent:

EVS

Excellent and logical suggestions for solving the balance problem, but I specifically want the QS pre, as I have QS amps and really like the sound. I was looking for a more technical answer in regards to simply using one channel, etc.

Rwwear have you seen the way the premier 7 handles balance control?

There really isn't a balance control that doesn't affect the sound adversely.

Just a guess, but some how I think you'd really go for a conrad-johnson premier 7!

I'm not a rocket scientist, but.....why not just get a pre-amp w/a balance control? Lots of good/great pre-amps out there. I have a C-J PF-R pre-amp (SS) w/balance control that I really like.....

I asked the same question for different reasons in a separate thread. They asked me what I was smoking. (I wasn't smoking anything (at the moment.).)

Why can't you just move your chair off center? Or your speakers?

There are many amps available with variable input attenuators. Achieves the same desired effect with a single pre.

Just get an attenuator for one channel . this can be a fixed value or variable and insert it between the preamp and amp on the side you do not have hearing loss. A balance control.