audio research

My experience is simillar to Thorman`s, I owned the SP-9MK2 for about 15 months(durning the mid 1990s). I found it to be rather thin. flat and electronic in character, I replaced it with a Quicksilver full function(all tube) preamp and it was a much better preamp, more dynamic,vivid,better tone,harmonics and more natural sound. I`d consider something else in the AR line.

Any version in the SP6 and SP8 family.

I would avoid hybrids. They just don't sound right to me.

Paul, I just noticed that you want to stay within the ARC line for your preamp.
The SP10 was the preamp that was available at the time of the D70's. I think this is a great preamp if you can find one today. It is hard on tubes BUT has an excellent phono section and IMO is superior to the SP11, 9 or 8.
Like it almost as much as my CAT..:0)

There was much controversy on the SP-9 with conflicting reviews when new. I auditioned one from a dealer and thought it sounded wonderful. The one I bought was sealed in the box and did not sound nearly as good, so I returned it.

I never followed up on differences between different ARC versions but my recommendation would be never buy a SP-9 without a trial audition in your system.

I prefer the SP-8 over the SP-9. The SP-8 can be notably improved by replacing the Rel-Cap coupling capacitors and bypassing the opto-coupler in the mute control.