Which preamp for Quicksilver mono amps?

I use the 6922 version QS preamp with my Mono 120s, and it's a great match. I also use an Audible Illusions M3B but have to use line attenuators to knock back the gain. This combo also sounds awesome. 

I use Aric Audio Super 6sn7 linestage with my QS mono amps. Stunning sound.

I have tried multiple preamps with my QS mono 60's. A QS Line Stage, a 6SN7 preamp similar to the deHavilland Ultraverve III, a ChiFi preamp based on a Pass design (very quiet, clean, cheap), and another DIY preamp based around a hi quality Burson op amp. All sounded great. I prefer the 6SN7.

I use the QS 12at7 line stage with my QS amps. I find that it has way too much gain ( 18db )for a line stage. It is a very basic preamp and does not have a balance, mono switch and remote. If these features are not important to you I doubt that you would go wrong!!

If you want your QS monos to sing, it's really worth trying some different preamps with them. While I've helped a few friends with the standard QS line stage, and its a value for the $, do try a few nice lower gain (or switchable) 6SN7 preamps at least, you might be pleasantly surprised. I enjoy an upgraded Cary SLP-98 with my own QS Mono amps. Same as what @hilde45 mentioned above, give it a try for sure.