That's the problem with all of these "What's the best _______?" type of questions. They presume that someone has experience with a wide variety of _______ from which to make a comparison.
I know where you're coming from. About 99.99% of everything I post on audio forums gets ignored. I don't bother asking questions here when I'm in a hurry. I usually don't ask at all unless I've searched the entire Internet first and came up empty-handed.
Those TEAC tapes with the metal reels are pretty rare, but yeah, too much. I've noticed Ebay sellers are selling brand new D90s that you can find in any dollar store for a couple of bucks per tape now. Feckin' vultures! Glad I stocked up on tape a couple of years ago.
There's some masking going on between the flute and another instrument playing the same line in the first part. Maybe push the one on the right back by cutting a little high end off of it.
The drums sound rubbery. You need more hit (close mic) and less tone (distant mic).
I've never used the modern powered monitors that seem to be a mainstay of home recording, but the AudioBox is designed to send its output to that kind of monitor over a pair of TRS cables, yes.
I wouldn't say worthless, but it is overkill. The main reason for sampling higher than 44.1 is so the brick wall low pass filter can be placed well above the audible range. (Yes, some people can hear the cutoff, although those people should be relatively few.) 48 kHz is sufficient for that.
I didn't research it thoroughly before I bought it either. I had an M-Audio card that had line level inputs before and assumed they all had them.
A MIDI cable is just called a MIDI cable. Someone at the store will know what you mean.
A MIDI connector isn't the same as XLR. Different number of pins. The little 2-channel AudioBox won't accept line level inputs at all. You'll overdrive the crap out of the mic preamp if you plug a line level XLR into the mic jack. It's very much a one trick pony.
It's a well-built device. It's probably great for mics and guitar. If you want to record keyboards or mix down from an external mixer into the computer, you'll need to get something else.