IF you want a project, there is this:http://users.skynet.be/myspace/mdsr/
You do have to do some minimal electronics work, and spend a few bucks. The result will be that you can use a "SDR" type DSP to give you the brickwall filtering, NR, etc. It's really pretty easy to implement. Here's the Yahoo group http://groups.yahoo.com/group/mdsradio/
If you are just looking for some audio DSP software, the good old DSP-Filter software by JE3HHT is pretty good. It's very utilitarian.
There is another one that is interesting, and more elegant, called BR-universal-Filt http://www.dsp4swls.de/dsp/br_uni_filteng.html
It has a fairly steep learning curve.
Then, of course, there's always VA3AGM's DSP Filter http://www.qsl.net/va3agm/index1.htm
And for your microphone, try http://www.dxatlas.com/VShaper/
I have played with all of the above. All require some adeptness at tweaking your soundcard configs.