Hi TEM. As a motion picture soundman in a "former life", I totally agree with Steve's (aka ironbut) advice. One additional problem with trying to record a specific "sound" during filming is that it will be YOUR preference for that scene - not necessarily the Director's or Producer's. With a clean original track you can go back and re-equalize to whatever their highnesses desire.
A second problem is that of "the weakest link" -- the delicate nuances you describe in your post may very well not be within the capabilities of your final playback medium to reproduce. You describe the project as a "low budget movie" so I assume the final product will be in either 35mm or 16mm film - and for "low budget" I assume probably 16mm or at least not one of the major-studio 35mm release formats. Any of the machines you mentioned have noise floors miles below that of your available film playback formats. Likewise, the machines harmonic distortion, saturation characteristics, frequency response, etc. all supercede those of the available film systems. A lot of what goes on in a film mix is cranking in corrections to make a track that is sounding good in a recording studio sound close to the same when played back in a movie theater. Even the best Hollywood sound engineers don't trust their ears to do this on location - they bring it back "clean" and "fix it in the mix". You will notice that, in The Tape Group, the first thing they did was set standards for a playback system of exceptional quality and then used it to judge their original material. Unfortunately, you don't have this option. You will have to learn the weaknesses of the playback system the movie industry has determined to be "cost effective" and adjust your production system to it.
My additional recommendation to those of Steve's would be to find an experienced film sound guy or gal who has had many of their location recordings translated into final release tracks and would enjoy working with you on the project. Pay them for their experience (and they probably already have all the equipment you need calibrated and ready to use) and collaborate. You can generate the quality of sound you think appropriate in your studio, play it for your engineer who can advise whether it can be reproduced in a theater and, when you have adjusted it to where it can, the two of you can sell it to the Director.
If, on the other hand, by "movie" you mean video format, then in some ways you have less problems and in some ways more. Most of the modern video formats are capable of reproducing better sound than the standard film formats, but they are played back in a far greater range of environments and on more diverse equipment. If video is the final format, then fire your mopic soundperson, specify the video format/presentation environment you want to optimize for and hire a colleague with experience making final tracks for that environment.
Good luck with your project!
Brian