I have a couple MXL 990s that I use for recording vocals, but they aren't much use in other areas. In front of my Blues DeVille they distort very quickly unless you move them back pretty far, at which point I get too much of a "room sound" from the amp. I do love em for vocals as far as dirt cheap condensors go, though. The 991, on the other hand, has never sounded good to me in any application. It may very well be the cardiod-pattern diaphragm module that is on the thing - I bought two MXL 604s and swapped the cardiod heads with the other heads supplied, and they sound great on my DeVille with the high-pass filter enabled, coupled with a Sennheiser e609.
All in all - I'd say the 990 is a good pick for a cheap vocal mic that isn't too noisy, and get the 604 if you want a decent multi-purpose mic (they sound decent on piano as well)
Well 2001 may not a good mic to some but good to other people and depends which application...but buying this pack you've got 603 (which is good) and a free 2001. Note the price of 603 is $99 also.