BAT or Sonic Frontiers w/ Martin Logans?

I also recommend the Mod3 which I've been using for 7 years now. Great phono section for the $$ if you need this. Two points, though: (1) Get rid of the Sovteks. Out of necessity manufacturers have to source tubes that are readily available in quantity. There are lots of NOS tubes out there that will sound better (using Seimens 6DJ8s)and let you "tune" to your tastes; (2) Be aware that this pre has incredibly high gain. Not a problem with some amps but can be frustrating with high gain amps. Not a sonic problem, but limits fine adjustmant volume and balance. Good value on the used market and with only 4 6922/6DJ8's you can afford to experiment with higher quality NOS tubes.

I'm using a VK-3i with my Magneplanar 1.6QR's also. I found that the preamp benefits from using good NOS tubes - I settled on Amperex Orange Globe 6922's after trying various brands and substitutions. The 3i is very neutral and sounds great but I wouldn't describe its tonal balance as being "warm".

I am using a BAT VK3i with Magneplanar 1.6QRs, so while I can't address your specific match, I can tell you that this is a very neutral preamp. I don't notice any particular character, other than the fact that music from my system just seems to wash over the entire room. FYI, amp is a BAT VK200 (solid state).

I'm currently using a Sonic Frontiers Line 2 and Conrad Johnson MF2200 amp with aerius speakers. Yes, the Line 2 is not going to add "tube warmth" but this combo is very neutral and detailed. Especially musical using balanced outputs.

I'm using an Audio Research SP14 preamp with (2) Classe DR8 amps, makes the Quests sing real nice...

I have Martin Logasn Quests that I run with an Audible Illusions Model 3 preamp and a McCormack DNA-1 with SMc Audio's Level A+ mods. Interconnects are Sysnergistic Research. mSpeakers are bi-wired with Kimber 8g. I get great warmth, but incredible imaging and detail as well. I second the recomendation to take a look at Audible Illusions.

A Line 1 isn't going to add a great deal of warmth. Even with NOS tubes mine is still pretty neutral sounding. I have no knowledge of the BAT, but will suggest adding Audible Illusions and Cary to your review list if "warmth" is the goal.

I have a pair of Martin Logan Sequel II speakers with Sonic Frontiers Line 1 and Power 1 amplification. I auditioned the BAT VK 3i and the Sonic Frontiers Line 1. Both units offer excellant quality, good value, and similiar prices and sound quality. After all of my searching for a tube preamp, my choices were between the BAT and the SF. I was in a quandry when it came time to purchase. Ultimately, my decision was made when I purchased a dealer's demo unit at an excellant price. I think you'll be happy with either one. Good luck!