Audio Research SP16 annoying volume control

The problem you identify is one I also experienced, mostly because I am using high efficiency speakers. There simply was not enough flexibility when listening to high output sources (i.e. CD's) at low volume levels. The good news is that it is an easy problem to solve. Send your unit back to ARC and have them do their "gain modification" which simply involves dropping a high quality resistor in whichever source you would like to shelve down the preamp output. I only did the CD input so the mod was called the "CD only gain modification". Now I have much more flexibility when setting the volume during CD playback, particularly at low listening levels. A secondary effect is that the volume is now matched for CD and LP playback. It cost around $60 if I remember correctly and they did a thorough check up on the whole unit while it was there.

My dad had the 16 then jumped a few steps and bought the Ref3, with efficient speakers it was an issue but was tamed by attenuators that shaved 9db off signal, some are a sonic compromise and some get pricey but have little to no negative affect..........Rothwell makes a model some like and some avoid but they are not pricey to try.
PS The Ref3 has a volume NOTHING like the 16,,,,,,,for $10K it better not!

Mating a preamp with an amp, you need to consider several things, such as gain of preamp, gain of amp, amp sensitivity, preamp output impedance, amp input impedance.

What Audiophile have said is very true (maybe with the exception of in/out impedances). I would also throw in a mix sensitivity of your speakers and output voltage of your CD player (I had this problem several years ago when I was using Theta Gen Va which had a generous, 6V output voltage).

To remedy the situation, you can (in general) do one of the following:

1. Reduce the output voltage of your CDP
2. Reduce gain of your preamp
3. Reduce gain of your amp
4. Reduce the sensitivity of your speakers

Reducing gain of your preamp seems to be the easiest thing to do (for example reducing sensitivity of your speakers would basicly mean that you would have to buy different speakers).

So if I match the pre-amp to a ARC power, then I presume that this would fix the problem?

Matching to an ARC amp will not necessarily fix the "problem". You either need to step down the output from the high level sources as I indicated above or buy one of their newer preamps, such as the SP17, LS17 or LS26 which have more steps (nearly double) in their volume control settings. Of course you could choose to leave things as they are and enjoy the music albeit without the ability to adjust the volume exactly as you like.