There's nothing wrong w/ the fastrack pro for the level that it's at. i'm suspecting user error, or bad room acoustics. so lets start from the top. so your bass is in good working condition, tuned, and has new strings, new battery if it has active pickups? there's no buzzes from the bass or the cables?

okay, pluggin, make sure the mic/line switch is in the right position. now gain staging, turn the volume on the bass up all the way. turn the gian knob up slowly from completely off, till the ableton meters are reading around -18db, thats about half way up in the meter. You should not see any red, or yellow.

this assures i nice strong signal from the bass, and plenty of headroom, in ableton, which is a must in DAWs. the tone your going to get is gonna be pretty clean, plain sounding. this is were tastfull settings in guitar rig come into play. also try the ampeg svt uno, pluggin, it's free and sounds nice.

unless you have a nice studio room, you're probably gonna do more harm than good, trying to mic your amp. remember, 90% of bass tracks recorded, are, di. this may or may not be blended w/ a mic'ed signal, but DI is the most common way by far. i mean your not gonna sound like james jamerson, but you can get perfectly usable bass sounds by doing what i described. good luck