Ive just started using the Digi mod UA-5 for ADC after my Sax and I like the intial results.
I agree with Brian dont bother with the W-mod if your running the oade pre in front, just get the D-mod if ADC is what you want the UA-5 to do. I think, but Im not really sure, the only mod that improves the analog in is the + mods.