the bass does not sound muddy to me at all. You can mess around with the attack time of compression to see if you can make it more punchy, but it sounds fine as it is.
To get the best resolution, there are some things to keep in mind.
THe resolution you have is good. TO get it better will require a substantial of amount of money that most probably will not make a difference to the person who is buying your CD. What the people want is a good song, nice vocals, big low end and rhythm.
If you are transferring to your computer via 4 track, make sure that you record initially at 24 bits and also record into spdif via 24 bits with the best and shortest cable you can afford. With spdif there is an slight difference between 15 foot and 3 feet.
Record as hot as possible. As close to cliping as possible without clipping. THe difference between a -1 signal and a -12 signal is 2 bits, so on a 16 bit sound card you are only getting 14 bits at -12 which is not very good.
Do as little editting as possible since 16 bits does not respond well to editting.
I was listening again and I thought that I should mention that there are commercial Cds that sound about the same. THe quality is good. I really lik the vocal. The singer has a really good voice.