Once your vocals are recorded, you're probably gonna want to compress them. This makes the loud parts quieter and the quiet parts louder (in a nutshell.)
Compression often makes a part (or vocal) sound subjectively much louder. 99% of the vocals you hear on the radio have been compressed, sometimes multiple times.
Pro Tools's built-in compressor is okay. The built-in BF76 is also okay. For starters, try using those to pump up the volume of your vocals.
The KSM27 puts out enough signal to certainly be usable (I've recorded vocals and drums with one) and the Mbox's preamps should have enough gain to five you a decent level.
As
MASSIVE Mastering hinted, in a perfect world you'd have a separate mic preamp (probably with a compressor built in) which you would use instead of the Mbox's preamp. Of course, in a perfect world, we'd all have Pro Tools HD Accel systems, Avalon and Universal Audio preamps, Neve and API EQs and Apogee, Prism or Sytek converters!
But here in the real world, the equipment you have should be able to let you lay down a decent song, once you learn how to use it to its best effect.
-Hoax
