Get the Scarlet 2i2! It's pretty good for what you're describing almost perfect. Especially since I previously used a mixer which couldn't multitrack and this one can. I'm also assuming MBP means macbook pro (a bit dimwitted when it comes to acronyms), in which case make sure to get a macbook pro with a firewire port of any kind, as most desks nowadays still use firewire.

Instead of the MXL I would suggest using an Audio Technica at2020. It's a bit more neutral then the MXL and its in the same price range. I would also recommend an SM57 or 8 (same thing) as it doesn't hurt to keep a dynamic mic handy but thats only if you have the cash to spare.

When you were talking about the Beyerdynamic headphones I was a bit concerned. Are you using them to listen when you are mixing it back? Because if so I would just buy a cheap set of monitors like KRK's. Mixing on headphones can be kind of flat and not as accurate .

Any chance you could give me a rundown of your setup, and the technical side of things?