Audio Research Preamp Experts?


Aside the from the notion that the latest is the greatest, which 3-4 ARC preamps from the past would be among ARCs best linestages? From the 3A forward. I don't care about phono performance, though I will consider the preamp even if it has phono built into it. Any sleepers from the past to compete with today's linestages?
pubul57
SP10mkII (more tubey), SP11mkII (more neutral). Though in general not as resolute nor quiet compared to their current breed, in top operating condition, they will still hold their own nevertheless.
I understand that the SP16 was based on the 6s with there use of 12ax7s, is the older version a better sounding linestage, or did the improvement in parts surpass the older model, even though the 16 was an entry-level model. I also understand the LS5s are outstanding. The marketing engine says things are getting better, but I really do wonder some times.