Why not have a look at a Rode K2? It should easily come in your price range.
They're lovely mics, and in my opinion work really beautifully on vocals and acoustics. Don't be put off by the surprisingly cheap retail cost, they really are excellent.
When it comes to choosing mics, you can get as many suggestions as you like, and as many recommendations and opinions as there are going, but when it comes down to it you need to choose one you're happy with. In my book, you really should hear all the mics you're considering before buying, and then make your decision based primarily on that. Always try before you buy!
When it comes to pre-amps, there are differences between them of course, but generally they don't appear as audible as the difference between different mics. So I'd invest in the mic you like the most and an mbox pro 2 will certainly see you well on your way, the preamps aren't top of the range, but they're fine. I own an mbox and it's served me very well.
Besides, if you get a mic you're not completely happy with now to go with the mbox, if you come to upgrade your setup later then you'll want to upgrade both the mic and interface/preamp. So why not just start off with your number 1 mic of choice anyway?