Is Audio Research SP-6 considered a good model?

There were so many versions of the SP-6, and not all of them were considered good, that it is really difficult to answer your question. If it is the original 6, it could definitely be improved with cap and resistor upgrades for probably not too much money but you have a competent technician do this work. ARC will charge you an-arm-and-a-leg to do this and I really can't say if this would represent good value (but I doubt it).

ARC estimated $700-800 for the work. I know there were other models with letters e.g. SP-6A... don't know if there were different versions of the SP-6. I'm also wondering what power amp would pair well with the SP-6......

the arc is a great peice, put honestly your totem/plinius combo is so good, i can't help thinking you will get 'different' but to improvement. think really hard about this change, and consider that a balanced tonally accurate playback system doesn't jump out at you (refering to the tube amp's euphoric mid's). arc is great tuber gear, and more reserved than some, put play lots of big, complictated music and really scrutinize how your sysyem reacts....yes those simple recordings are gonna sound a little more holographic with the arc, but the soundstage is just part of longterm listening fun. in any case, best of luck

Well Jaybo thanks for the advice...I am listening pretty hard...I didn't find big orchestral music to be very well handled on either the Plinius or the ARC......I thought maybe in the case of the SP-6 that I didn't have enough power to fully exploit its qualities.....

i also think you might be impressed by the new cyrus 8 integrated....and the new creek 5350 (both compete and control well beyond their retails) .....well within your price range, and both 'a bit' livelier that the darker plinius character. comparing may help you sort this out before commiting....the forests are great, and your exposure player is also a giant killer.