I owned an ARC SP-11 Mk 2 for many years. It was the first of ARC's hybrid tube/solid state preamps. I would call it more neutral than the SP-10, tending more to the solid state sound than the 10. It used 6DJ8 tubes, and had some ability to tailor the sound by having separate gain and volume controls that used the tube and solid state sections of the preamp--you could have a tubier sound or a more solid state sound by playing with these controls. The SP-11's phono stage was pretty good, and I recall it also had a mono switch and balance knob, which are things that I wish manufacturers had not done away with. While the SP-11 was at the top of the heap in its day, it is probably a bit dated by today's standards, though still a quality piece of equipment. Ultimately I gravitated towards Jadis and Shindo preamps, they had a more classic tube sound than the ARC that I preferred.
I would second the VAC Renaissance recommendation as a possible alternative to ARC, if you're looking for full-featured preamp with a more tube-like sound. I had one in my system while my Jadis JP80 was out for repairs and thought it was something special.