I have the L-1 and it mates very well with my McCormack DNA-125.
One thing you need to be aware of is that the McCormack amps are a little bit sensitive. Not a problem, they just are. So don't yell at them! Seriously, you want to look at pre's with lower gain or those that have gain controls like the L-1. (FYI - your front end output also figures into the mix, I think 2 volts output is considered average??)The Blue Circle mentioned above I think has 28db of gain, way too much for your amp. Not sure about the Rogue or Audio Research. FYI - The L-1 has alot of gain but since it has left and right gain controls it is not a problem.
I currently have an Eastern Electric Mini Max for demo (great pre!)and it has 20db of gain. I cannot go past 9:00 with the volume control. It does have a smooth volume control and not steps which helps so this is something else to look for. If looking at a pre with a stepped volume control, the more steps the better as it gives more "volume settings" than lesser steps.
Passives are also pre's to look at. Usually more detail, transparency and tonal accuracy but many say at the expense of dynamics and musicalness (word?). I had a passive but like you wanted tubes as I wanted the fullness and bloom of tubes. The passive sounded flat to me even though it was more transparent and detailed with better separation.
There are alot of good pre choices for matching with your amp. Relax and enjoy your search.
Regards,