Who out there knows about Audio Research Pre's???

Out of all the the used tube pre's which one offers most bang for the buck?Also if it is the SP6 how much odes the A version differ from B-E?I notice a number of LS22's which seem more recent in vintage and list for $4K going for $1500 and they look form back to be fully balanced (though looks/XLR's can be decieving).How old are they and why do they go so cheap.The LS25II seems to be most recent and uses the 6H30 (??) "Super Tube" like BAT.Seems a bit to rich for my blood.But want something to replace my Muse at some point to match with a Mesa Baron and about 10 different spaekrs I will own over next few years.
any input on the sp16 l
I have listened to both the SP-10 MK2 and SP-11 M2, clearly the two best vintage preamps from ARC. I find the SP-10 MK2 to sound warm and tuby, and when compared to the SP-11 MK2, it lacks the high & low end extension and sound a bit too syrupy & dense in the midrange. However, when matched with a leaner system, it could sound very inviting. The SP-11 MK2 has a cleaner, bigger, faster, more detailed and more dynamic sound. Its midrange is more neutral (just a bit tuby) and very liquid, but not emphasized like that of the SP-10 MK2. Furthermore, the SP-11 MK2 in terms of bass slam depth and speed is far more impressive. Overall, the SP-11 MK2 has a more linear sound with a blacker background.

The better preamp? I believe that it depends on what you have. If your system, independent of the preamp, tends to be lean and/or bright, the SP-10 MK2 may be your road to salvation. If you have a rather neutral or warm sounding system independent of the preamp, I would prefer to go with an SP-11 MK2.
The SP-16 is very good for the money. It is a bit more tubelike than some of the ARC preamps. It has nice bloom and air. Stay away from the LS-7,15, or 22. All sound too thin and sterile for my tastes even though still better than solid state preamps in their price range.
Call Dave Gordon, at ARC, and tell him that Larry Staples told you to call directly.
Dave is a square shooter who will be completely above board and helpful. I have known him for almost 20 years. He will definitely help you.
Good Luck,