Right now I have a pretty underwhelming set-up: Sony ECM DS70P mic and Sony MZ-NH700. Yes, I know--a MiniDisc. I don't get a chance to tape that often anymore due to my being away at college. Though when home for break, I noticed my MiniDisc finally kicked the bucket. My biggest concern is the actual recorder, with any microphones or pre-amps being secondary. I got some real nice captures with that set-up, but since the actual recorder is past its time, I need to upgrade.
The M10 is a great choice for a recorder, but if you buy one and run your Sony ECM DS70P mic into it, you may not hear any difference in your recordings. Mini-Disc quality is surprisingly good as long as you aren't using one of the long play modes.
On the other hand if you buy a Church Audio mic and battery box and run it into the Mini-Disc your surely will hear an improvement in your recordings (unless the Mini-Disc is no longer working properly). Church mics are a huge upgrade to your Sony ECM DS70P mic. A Sony M10 is also a huge upgrade to your Mini-Disc, but the change in audio quality may be hard to hear. When I recorded with a Hi-MD, I used the High LP mode (which is equal to the best standard Mini-Disc quality) and the recordings sounded incredible. (I didn't use Hi-MD quality because I could hear no difference and didn't want to have to swap discs during a show).
Unless you are big on using a recorder's internal mics (which I don't recommend), if you can't afford to buy a complete set up right now, I would buy your new mics and battery box first and a new recorder when you can afford it.