I have the same amp and once I listened to my cd player (has it's own volume control) going direct to my amp, there was no turning back. Going direct revealed several layers of musical intimacy and resolution that I was missing. And I had been using an award winning tube preamp costing $3000.
The only problem with going direct permanently in my rig was that I use a Fathom sub and secondly that I have multiple sources. So I decided to get a preamp that was as transparent as possible which led me to Placette Audio.
I ended up with a Placette active preamp and I am very satisfied with it. It is my last preamp. However, even used it is out of your $2k budget, so I would recommend the Placette passive preamp. You would need to do some research to make sure that your system is compatible with a passive preamp both electronically and musically. It is very revealing and exposes component mis-matches. Plus your cdp will need to have enough muscle to drive your amp.
