gday cens......I don't know the specifics of your player, but the addition of a low jitter clock circuit as you mentioned is imho absolutely essential. There are a few brands out there such as audiocom, trichord, LC audio. If you want to roll your own try elso kwak's latest version 7...it is an ear-opening improvement!! if you like the sonic flavor of your player as it is, it will improve all the things you like about it. He'll sell you a complted board but you can get most of the parts easily and a couple as samples from AD etc, so you just buy the little pcb and olay off him...(at a fraction of the cost and at least the same sonic improvements as the others).
You should also give any add-on low jitter clock circuit its own little power supply, which can be done in a small space and for <$25...I have heard the diff with and without a sep supply and I reckon the go is a sep unreg'd but well-filtered supply...most good clock circuits have on-board regulation. email me privately if you want further info.....no I dont work for elso, but his circuit is excellent, cheap and is truly in the spirit of diy.
You can also change supply caps (sub low z and selectively increase size...you dont need flavor-of-the-month boutique types to get better sonics) and coupling caps and also sub ultra-fast, soft recovery type rectifier diodes for sonically obvious improvements. check out audioasylum and diyaudio for details.
Ive just gone through this mod path myself and turned a horrible/screechy digital sounding cheap cdp I picked up on ebay for bugger-all, into a very detailed, dimensional imaging source with sweet extended highs, very seductively listenable analogue-like mid range and fast, extended, very well defined and rivetting bottom end. The soundstage is bigger and individual sounds are easily identifiable and steady within their own part of the sound space. End result is a very enjoyable and engaging musical experience...its not perfect but in some ways I prefer it to my Linn/moddedRB300/Blue Point Special setup...and thats a real sonic compliment~~
cheers........cb