I should clarify, the units I listed were possible alternatives to Minidisc. If for some reason you decided you didn't want to go Minidisc. (There's a lot of MD haters out there, hehe)
I was comparing them to the current
MZ-RH1 which is arguably the best MD unit ever made. It goes for around $350 street. The MZ-M200 is just an RH1 with a bundled
ECM-DS70P stereo mic, and goes for around $400. These are going to be the only MD units that will be easy to find brand new, because all other units are out of production AFAIK. If you don't mind cruising classifieds, eBay, etc, any Hi-MD unit with a mic-in jack will work for you. The
RH10/M100 is very popular because it has a nice big OLED display and an AA battery attachment. (I really want one of these myself) Expect to pay around $190~$250 for a mint unit on eBay. Finally, if you truly want to go budget, MinidiscAccess has a great deal on the NH700. It's the bottom-line budget Hi-MD recorder that has a mic-in. It does everything you need it to (PCM recording + uploading of resulting file) AND runs off of AA which is a plus in my opinion. Great deal on this one
here. Absolutely killer deal on a solid Hi-MD recorder.
Now having said ALL that... CSMR had some great advice. Choosing your mic first is a great way to approach this. I'm still going to recommend MD for you because you sound like you're kind of experimenting at this point. MD just represents the best value for you from what I can see. There are a ton of mic options available for plugging straight into the mic-jack. Then, if you expand to a battery box/preamp rig into the line-in, the sky's the limit. Ahh... sorry to be too long winded. It's just that I've been researching Hi-MD recorders for myself so it's all kinda fresh in my mind right now.
Edit: Changed the RH10 price to reflect what I've seen on eBay as of late.