sonic frontier line 2 se+

No. I own(ed) a SFL2 and cannot recommend it. It is really a better dynamic range compressor than a preamp. Very dry dull lifeless sound. There are dozens of preamps that will give you a better sound. It also has a failing volumn control that has a nasty habit of going full volume in one channel and has damaged a speaker's voice coil, so I had to have a woofer rebuilt. SF is also out of business, so I don't know why anyone would bother with legacy equipment. You already have a ML preamp,even being solid state, MLs are outstanding preamps.

Try something from Audio Research, even their lowest price line stage will be better.

6550c, did you buy your SFL2 new or used? Did you roll any tubes?

I had a SFL1, SFL2, Line 3SE+ and Power 3SE+ and NEVER had an issue. The pre(s) were used with many amps but mainly Krells (KSA100a, FPB300 and FBP600) and the Pwr 3, and they sound fantastic with no impedance problems.

Compare to the competition in the same vintage, I much prefer SF. I found ARC very bright, CJ too slow ... forget SS. I do agree in stock form, the sound is a little thin, lean, mechanical and dry. The SE+ addressed those issues and with the proper tubes, it's competitive with current competitions.

Chris Johnson founded PCX after selling SF and can service any SF gear at a very reasonable price.