If you run directly into a deck is it less likely to overload?
In terms of having clipping/overload on the output of the mv100, no it doesn't matter what you run it into. What you run it into only matters in trying to determine what you're overloading, if you're hearing that distortion on your recordings.
The mv100 supposedly can output a 15dbu signal, so with typical condensor mics (say ranging between 7mv/Pa to 20mv/Pa in sensitivity) you will be able to record in settings with sound pressure levels in the 120db to 130db range without clipping the output of the mv100 (assuming you're at 20db gain).
Your recorder or A/D can also overload if fed too hot of an input. The mv100 can put out 15dbu, so you're recorder/AD will need to be able to handle that hot of a signal. The D50 can for sure (I think it takes up to 24dbu), but I don't know about the R09.