Here's what the mods do in no particular order, and this is all repeated from what I have read. I am an insurance guy, not an EE. Basically all of the mods are changing the capacitance in the signal path. By increaseing the capacitance, you are allowing for greater flow of electrical signal, which is essentially what the transport does anyway, not unlike any piece of playback gear. Most if not all of the capcitors are replaced in the power supply part of the board. If looking at it display side towards you, this would be on the far right hand side with a white outline around it. The power supply becomes much quiter, as no noise is being generated which degrades the signal path. The second part of the mod is changing numerous caps in the analog and digital circuit to allow for increased current flow. Again, reducing noise and making for a much quiter signal.
Now, the mod that will most likely effect exactly what you are talking about, feeding a DAC, the question becomes are you going to feed it a digital or analog signal? If feeding a digital signal, the mods above drastically improve the units performance. If feeding an analog signal, which I honestly have never used, an analog bypass aka swenson mod is the best way to go. By attaching some hook up wire, preferrably something that isn't garbage, you will be able to bypass much of the extremely noisy analog signal path, and feed it directly to the outputs of the rca. This is done by putting a couple auricaps, sonicaps, whatever to incrase the signal to a line level signal strong enough to compensate for the gain stages you are bypassing. This is a marked improvement for the nalaog signal from what I have read.
The other mods I would like to perform here in the near furture are a derivitive of the ones BOBM came up with.
I am planning on doing at least one unit with all blackgate caps, which are a marked improvement over their panasonic counterparts. They are also four times as much money. I am determined to figure out what the differences in caps is, and apparently you can hear the difference, we shall see. I would also like to change out the opamps in the digital path to something with a much higher slew rate, possibly the same ones doug uses in the t-mod if I can figure out the part number, which I have narrowed down to two. There is actually a newer opamps which I might try. I have never switched out opamps, but will give this a go to see how feasible it is in changing digital signal path. Finally, if you really want to get creative, adding bybee's to the outputs of the 4960, specifically the digital and picture outputs would be extremely beneficial. However, adding 150 bucks in parts for the bybees alone may not be the brightest of ideas. Oh, one more...if I had a dremmel tool, which I do not, I would probably attempt to add a IEC connection on the back and get rid of the garbage power chord in favor of a ven haus or bolder pc that would improve the unit as well.
In summary, is the unit in it's stock form any good? Sure, or we wouldn't be using it for transports in the first place. Can 150 dollars help it to rival $1000 transports, yes, indeed it can. You could even take all of this a step further, adding a superclock, rewire, etc, I am just not willing to take the time involved to attempt all of that! Yes it will help, grace dac or not!
I hope this helps,
Daryan