I will chime in with a very different response to the ones above. The SP-8 was ARC's first preamp that brought on awesome 3D and body to the instruments and harmonics that was simply not heard before. This carried on with the SP-10 but unfortunately went downhill until the LS5 came along in 1994. Sadly, only a handful of ARC lines stages or preamps have continued on with this performance over the years.
Comparing an LS2 to an LS25 and thinking the performance improvement was due to the newer tube or newer technology, well, it's not that easy? Why? Because the LS2 was just about ARC's flattest line stage ever. It and the LS15 sound like broken toys when put up against the LS5.
As for the LS16/17 series, marketing hype aside, if you want to retain the 3D strengths of the SP-8, you're going to have to go for an LS5 or LS25, Ref 2 on up. Finding a tweaked/modified older unit, maybe by GNSC, could be your ticket to keep what you have with the SP-8 and get some new refinements such as more coverage at the frequency extremes and better low-level resolution.
Also, if money is an issue, put all you have in the line stage or preamp and keep the amp you have if it mates well with your speakers. There are many many good amps out there. I can not say the same about line stages/preamps.
If you are not in bed with ARC, look into good deals on used BAT products as well. In many cases, BAT products beat ARC at their own game.
Comparing an LS2 to an LS25 and thinking the performance improvement was due to the newer tube or newer technology, well, it's not that easy? Why? Because the LS2 was just about ARC's flattest line stage ever. It and the LS15 sound like broken toys when put up against the LS5.
As for the LS16/17 series, marketing hype aside, if you want to retain the 3D strengths of the SP-8, you're going to have to go for an LS5 or LS25, Ref 2 on up. Finding a tweaked/modified older unit, maybe by GNSC, could be your ticket to keep what you have with the SP-8 and get some new refinements such as more coverage at the frequency extremes and better low-level resolution.
Also, if money is an issue, put all you have in the line stage or preamp and keep the amp you have if it mates well with your speakers. There are many many good amps out there. I can not say the same about line stages/preamps.
If you are not in bed with ARC, look into good deals on used BAT products as well. In many cases, BAT products beat ARC at their own game.