As Elsneb recommends, running it directly into a preamp, bypasses the volume control, and thus gets better sound. The Resolution Audio Opus 21 is a very analog sounding cdp when used this way. It is the best of the units I found in the under $4K range. However, to bypass the volume control, you must pony up some more cash and get a DIN output cable, as the RCA and XLR outputs both go through the volume control. (FYI, I use the Audience AU24 cable for this application.) I find it to have very good dynamics, albeit not analog good.
And, I will readily admit that the Audio Aero Capitole II is a better CDP than the Resolution Audio Opus 21. (The best cdp I have heard actually.) I have heard them in the same system, as my friend replaced his Opus 21 with the AA Capitole II. It sounds even more like a good analog source. (As you can tell, I prefer the sound of analog to digital. And, even the AA Capitole II does not sound as good as a well setup analog source, IMHO.) And, the AA Capitole II costs double the Opus 21, so it should sound better. And, unfortunately, the AA Capitole II is double your budget. If you want the best, and must go directly into your amps, I recommend saving up for the AA Capitole II.
If you have a preamp however, the Opus 21 is a good way to go. (At least in my case it is, as I would much rather put the addition $2K that it would cost to upgrade from my (used) Opus 21 to a (used) AA Capitole II, into my analog system.
My two cents worth.