I've been wanting to do something with my Teac VRDS-9 for a little while. It doesn't sound bad, but I think there is more to be had from it. It uses 4 x PCM1702AP's. That bit doesn't seem so bad. I could possibly add a clock upgrade. I think the op-amps could be improved on(m523BL and 2114's) and it will probably benefit from swapping a few caps.
Now I could do this or possibly take the slightly lazier route of getting a Caiman or building something like the Gigawork dac available from ebay that seems popular.
Anybody got any suggestions?