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).
Is Audio Research SP-6 considered a good model?
I'm trying to decide on how to replace my Plinius 9200 with separates. I have a 70's era SP-6 and I'm wondering if it's worth servicing and keeping, or are there other tube pre amps (Audio Research or otherwise) worth looking for used (1-2K range). Also have a AR D52B that I will definitely be replacing.
Totem Forest speakers
Rega P3
Exposure 2010S CD
Totem Forest speakers
Rega P3
Exposure 2010S CD