Guys... All my tracks in my site (www.nikolas-sideris.com
), in the commercial section (not classical cause there it's only live) are made starting out with midi. Just go and listen.
I believe that this is rather realistic (there are better of course)... I don't think that midi sounds will cut it, unless it's realy heavily tweaked, PLUS midi sounds different in every soundcard. It may soun dperfect in you rsdouncrad and crap in another. This is why early games with midi had different versions: Adlib, soundblaster, rolland... etc...
Depends on why you want it man. If you want something "decent" you will need to spend a bit more than 40$. But it may not sound bad really. I've not heard it. The frequency response is not really great (what the mic captures), and it certainly goes low after the 10 k which is not nice... (humans hear from around 40 hz to 16 khz. but there are hypersonics above that which do give something and make a difference).
On the USB issue, I've never tried a USB mic, so I don't know, but the main thing would be latency.
Still on 40$, I don't think you can really go bad. Just buy it. (Or maybe I'm a bit deaper to what I spend generally), but 40$ is practically 1 game. So save up. It's not THAT much.
The alternatice could possibily be something like 300$ (audio interface + mic) so it's quite a leap...