The deck has fine pres on its own; the oade mod I have brightens it up a tad. I think it sounds better with DPAs and AKGs than Schoeps; I feel that the MK41s can sound a touch harsh on the Oade mod pres.
I like the USBPre2. Easy to use, good meters, light, easy to power, transparent and clean, and cheaper than the Grace boxes.
I run the Naiant littlebox into it with my KCY setup and while I admittedly do not like the sound quite as much as the SD box the price and convenience are hard to beat, and the transformers do good things especially with the MK41s. I've made great recordings with both though.