oppo 105d mod or look for a new cd player ?

I owned a Modwright tube modded 105 and yes it is way better and I'm sure you would enjoy it. I would however would look for a used Aesthetix Romulus cd player. This allows you to upgrade if you wish in the future to their signature series and it is a great DSD and 24/196 dac.

I think Chayro has a point ... Consider either the EAR Acute 3 or the non-DAC EAR Acute offered here on audiogon. You won't be disappointed in the sound quality of this fine design.

No affiliation to either seller. Just a Acute owner who'd like to see others enjoy a really outstanding sounding player.

Good luck.

Many great suggestions here! But my vote is for a high end CD player. With under $4k you can get a very fine stand alone SACD/CD player, like one of the Esoterics, the Ayre, high end Marantz, personally I just got the Cary 306. I thought my Sony was high end, until I heard the Cary! And it has D/A in and out, so it's DAC can be used by other gear, ie computer. Keep the Oppo for playing all other formats, and buy a used CD player of the high end variety. A few reviews should help you decide which ones might lean toward your tastes. My 2 cents, worth about a cent and a half.

At ZD 542
I am unfortunately deeply aware of the DAC as a critical piece of gear to the new(er) generation of audiophiles. I am active on Head-Fi where I would venture a guess that the vast majority use computer servers and the audio component of choice is called a DAC/AMP.
Yes in view of this trend the industry is now paying serious to DACS are they are very very important. It should be noted that the Head Fi community does not buy very expensive, high end gear, probably because most are young and just starting to amass their fortunes I still use a CD player for much of my music with the so so dac and it's fair transport. A consequence of a miserable divorce, with a huge change in my living space and income will make getting a truly fine CD player a questionable endeavor. If I follow the pattern of a head fier I too may end up buying only a dac. My previous comment reflected a situation when I was buying good CD players. I even have one my ex won't yield out of spite.

Personally i'm waiting on the future replacement for the Oppo 105 (not the Super Darbeen version, or whatever dinkee update comes out in the meantime), then I might send that to Dan for the full truth mods (just to spin the occasional SACD & play dvd's). But to answer the OP's question, I would look for a 2nd hand Accuphase DP-75V..gorgeous looks & still a classic. They can be found for about $4k in good shape if you're patient. Here is a link fyi - http://www.accuphase.com/pdf/dp75v_e.pdf