Audio Research SP9 family

I want to know more about the Audio Research Family. What are the differences among Mk. I, II and III? I learn that the SP-9 family uses only 2 6922- does it mean that the SP9 use tubes in the phono stage and transistors in the line stage (like SP14), or one tube for the phono and one tube for the line? How well was the SP9 accepted when it was new? How does it sound? Is it a good value?
ARC SP 9 MK III is the best and as all the SP9 uses two tubes , one for the line stage and one for the phono stage. MK III is the only one that uses 6922 the previous models use the 6DJ8/ECC88.
I had the original SP9 and have upgraded it 1st to a MKII and now MKIII. If you have a need for a very good phono stage at a reasonable price the SP9 is ideal. The upgrade to MKIII GREATLY improves the line section too. It brings it more into the "LS Level" preamps I use it in a system with maggies/velodynes Audio RFesearch AMP and Theta Digital and VPI Jr