Crown : answering your qns first ..
1.)midi is just data of your playing, it has no sound. so you may play on electronic drums now but changing the sound module to that as if you're playing percussion or even some hiphop drum kit is infinite, so it's the "sound module" you're using for your midi playing. some orchestra for example may sound digital and fake, but (volume automation) controlling the volume manually for each "virtual player" or add reverb/compression may add some kind of "life" to it. so this is where mixing also counts
2.) hardware mixer has capability to add EQ/reverb/pan BEFORE it gets "recorded" (if you use it for recording) , but if you make a mistake in the EQ you cannot work with that track until you re-record it again, so most ppl will usually record it "raw" or "flat" first, then apply that in software (DAW-digital audio workstation a.k.a "SOFTWARE MIXER"). that's why nowadays hardware mixers are commonly only used in jam studios and live.
3.)in recording situations, the "software mixer" (DAW) is used DURING recording, but people have the misconception that to record you need a HARDWARE mixer, which is pointless because you record using the hardware mixer's PREAMPS ONLY, and then you start eqing panning etc later on in SOFTWARE. as I answer these questions re-read the DIY Recording FAQ and realise you can relate to it more and more.
so the stages of recording is usually :
1) PreProduction : jamming to the song, getting the feel right, finding out what tempo works best. is the song finalized or more creative touches can be added at this point?
2) Recording : drums(overhead,overhead,snare,kick,tom,tom,tom),guitar,bass,vox etc.. into individual tracks.
3) Mixing : putting those individual tracks together as a "stereo.wav" via compression/eq/reverb/etc. but not exceeding the 0db limit (above 0db = distort/clip/overload)
4) Mastering : final touch up of the stereo.wav be it making it louder, or a final EQ or final compression, warmer,audio exciter , noise cleanup , etc.
4.) FMR RNP is a great preamp! of course that one is better than the firebox but the firebox now is your ideal situation, I'll be right to say that if you kick ass with the firebox preamp , in future if you buy a better preamp you got no reason to sound worse right?
Now here's my problem questions :
i forgot to ask, does your midi controller have a USB input? if already have, then you don't exactly need presonus firebox. cos after I read what madwerewolfboy said, I disagreed with his recommendation initially because Zoom H4n does not support midi, but reading it again , I realised if your midi controller already has USB support, you don't need firebox's midi inputs. cos you only need the 2 preamps of the h4n (which is pretty good too). however this one would be your own dilemma ...
1) if you bought Zoom H4n at $428 :
Pros - you get portability, you get 2 XLR inputs, and you get 2 onboard condenser mics and USB audio interface (you didn't mention whether your mac has firewire inputs?)
you could even record drums at jam studios using the 2 onboard mics as overheads + the 2 inputs for snare and kick. cos H4n records 4 track at once standalone. can even record your gigs or whatever.
Cons - you'll be stuck. no upgradability. but for your situation demo is alright. but take note, if you plug H4n via USB , audio interface mode, you can only use the preamps OR the mics. 2 channels only! (almost slipped my mind) no 4 channels!
2) if you bought the Presonus Firebox at $400 :
Pros - there's 2 XLR (preamp) inputs, there's no mics, but there's 2 line inputs (no preamp), which means in future when you upgrade and buy a FMR RNP or any other better preamp than firebox's, you can just plug into the line inputs and have 2 inputs of firebox preamps and 2 inputs of preamp of your choice. there's midi input too, if your midi controller has no midi > USB , or should you buy an electronic drumkit with midi output, you can utilize this midi thingy. so with 4 inputs , midi.
Cons - if you don't have firewire port, this is out of your league. if your midi controller has usb, then this one also quite pointless.
H4n cannot upgrade but achieves all your purpose. firebox can upgrade, but you still need to set aside cash to buy mic.
P.S : before you have the impression that H4n's puny mics are crap, here's a
recording (but with proper mixing) I did purely on the old discontinued H4 and the H4n now is even better.