To Clarify

the question is,

Is it all about the preamp, will that clean up the recorded sound and make a significant difference in quality.clarity.

The weakest link applies. Depending on the bass and it's sound quality, how well it is played, and what damage the soundblaster is doing. A great preamp would not shine as it would with a signal path that sounds like a cloudy day.

Im runnin line in from an acoustic pickup, and from an electric Bass into a mixing board, to a soundblaster in my comp.

This is an impedance mismatch problem.

The line input of the mixing board is probably a lower impedance than the acoustic pickup and electric bass.

In other words, you need a D.I. or a preamp with a built in D.I.

A D.I., or Direct Box, converts your bass or guitar signal (high impedence) to a line level signal (low impedence). It has a 1/4" input and an XLR output to run to the mic preamps on your mixer. Then use the gain or trim control on your mic preamp input to boost the gain to a respectable level.

Your sound should improve quite a bit.

Here are some D.I. boxes, in a range of prices.

http://www.8thstreet.com/product_search2.asp?combined=direct+box&Manufacturer_Search=Manufacturer+Search

what type of sound blaster are you using?

sound card

all i can find is Creative SoundBlaster Live (WDM)
seems like it would be Ok, thanks for all the help guys, any more info would be much appreciated.

Mic'ing

would using shure mic's help this signal problem at all, instead of just line in?

then would a Preamp with D.I. make a huge difference in the quality of my recording?

With mics and pickups, a preamp isn't just a good idea... it's the law. Any pre will be a very large improvement over your current setup.