To preamp or not to preamp?...that is the question

Check out the Theta Miles (about $1200 used), the Mark Levinson 39 (not sure if the model # is correct) or the Spectral SDR 1000 (about $2500-$3500 used)

If you want to drive an amp directly, this kind of unit works best if you can keep the length of the interconnect relatively short -- not over ten ft -- otherwise you start losing dynamics & impact; music can start sounding "homogenized."
Best of luck,
Joe

Avoid using CD volume controls that do it in the digital domain. Use ones with analog controls, or use a passive preamp with any CD player. This is tricky because of the impedance of the passive preamps with resistive volume controls. If you pick a passive preamp with transformer volume controls, such as Bent Audio or Silver Rock, you will not have this problems with impedance.

I recently bought a Resolution Audio Opus 21 cd player that has a built in analog volume control. I was prepared to keep my SF Line 3 but found the Opus 21 run direct much more transparent, pure, focused, and dynamic. The SF Line 3 had a little bit more body, but was noticeably less transparent, more diffuse, and the PRaT was greatly reduced. Some may prefer the Line 3's more relaxed presentation by comparison. My amp's sensitivity (.8v/47k ohm) and speaker's efficiency (91spl) are reasonably high. The Opus 21's output is rated at 2.5v SE and 5v XLR at 100ohm. I'm not sure what other factors are at play, but running direct in my system is more enjoyable.

I agree with Twl, an analog volume control is preferable to digital, as unless you run the digital volume with little or no attenuation (some Wadia models such as the 860 and 861 have an internal adjustment in the unit to enable you to do this more easily, I don't know if the 831 fits in that category) the sound seems to degrade. However, you should be sure that the analog volume control is as well-executed as the analog preamp you're replacing, which in your case will not be easy. Personally, having heard your system, I'd stand pat!