My two offerings:
<1> DPA MMA6000 preamp (no outboard ADC - use your MD). May not be real easy to switch from the (I assume) 1/8" stereo mini plug to 2 x microdot connectors, so you may be best of selling the mic/batt box kit and replacing it with new mics w/ microdot connectors + the preamp.
<2> Keep your current mics / batt box and replace your MD with the Edirol R-1 (a bit out of budget after adding a CF card - and I know you said you wanted to keep the recorder, but this is a great option)
I suspect others will chime in...