I have been using the Cambridge 851 CD player for a few years and want more.

I use an 851C as well and was pleasantly surprised how much it improved with the Synergistic Black fuses; there are two. I also run a Nordost Vishnu PC which really brought out how good this player is. No doubt a DAC could improve things, but I’d still recommend changing out the fuses first and if you’re using the stock PC change that out too before you spend money on a DAC. I also use Ayre mrytle blocks which also elevated the 851 sonically. Point is the 851 is a fine player that has more potential than in its stock form. 

What's ur budget?

I had an 851C for a while and originally sought it out based on the many positive reviews and, especially,for the built in volume control as I hate most preamps.  I was mostly pleased with it but found it just a bit lacking in detail compared to some others I'd heard or had.  I compared the 851C directly to an Upgrade Co Oppo BDP-83SE with the outboard tubed power supply and the Consonance Droplet 5.0 cdp.  I thought it slightly less resolved than the Oppo, though it was pretty close.  The Oppo had some tube magic though as well as SACD & DVD-A playback so, I'd pick the Oppo over the 851C.  The Consonance has tubes but has more of a lean/clean/clear sound than the Oppo but is noticeably more resolved displaying a greater degree of inner detail and just being more of an open widow on the performance.    I've also recently acquired a Raysonic 228 and find it to be at least as good as the Consonance.  I mention these players as they also have built in volume controls and that's all important to me as I always run my source directly into my amp(s) for the least sonic degradation.  I'm all about transparency and detail.  If these aren't the qualities of the 851C you prize and would like to further on, then my recommendations may not be applicable to you.  Also consider these players are about a decade old so may require replacement of lasers/transports. 

Remember, Oppo is going out of business.

Hi Soix,
My budget is around 2K, although I often don't stay within budget.