The mxl 603 is one of the best mics for accoustic guitar under $500 I can think of. It's one of those rare audio no-brainers.
I've owned the mxl v67, as well as the mxl 2003. The v67 I liked at first, but after a while it kind of fell out of favor -- a little muddy and indescript . . . not very smooth or present, and the pickup pattern is so wide as to border on omni . . . so not a very tight or focused sound, either. The proximity effect is so exaggerated as to make it nearly useless without a lot of bass-cutting. Probably just the thing, though, if you have a super-wimpy mousy kind of voice, I suppose.
The 2003 I liked somewhat better, but after a while, I sort of noticed it's just a very bright mic, and not particularly smooth, either, particularly in those high frequencies. Not nearly as bad, mind you, as the 2001 or some other cheapy condenser, mind you, but still not to my liking.
They've both been gone for some time now, but the 603 remains one of my favorites. I've never been unhappy with a single accoustic guitar track, and I like them as drum overheads on occasion (when I need a brighter, more defined cymbal or hi-hat sound).
The one I hear about a lot these days from some of my comrades is the v69. Supposedly a surprizingly good, inexpensive tube mic.
