How about have a close look at the M-Audio Microtrack II? I have been using it solidly for the last couple of months and it is really nice. I am not sure if its too much for your budget, but when I saw some of your requirements of a portable recorder I thought I should share.
The Microtrack II records to Compact Flash and does also have a USB interface. I know Compact Flash isn’t SD but the price of the media seems to be fairly similar and the slight size difference (bigger) doesn’t bother me at all. I have an 8gig CF card and it can record so much more than I need in one session.
The recording options are great, you can choose between 16bit and 24bit, and from 44.1kHz, to 48kHz, to 96kHz. I noticed you said you may sometimes use a lapel microphone. The Microtrack II has a stereo minijack input, as well as two balanced 1/4inch inputs (which is great when you’re using higher quality microphones) and also 48V phantom power for powering quality condensor microphones.
Another thing is, you can always start with a cheaper microphone, and then get a better one later, but the Microtrack as a portable recorder is really worth the price.
Spencer Sternberg
Audio for Games
https://www.spencersternberg.com