You can get any number of opions (mic-pre, condenser mic, etc)
Most importantly, you need to ask yourself, what is wrong with the recorded product. If you think your final product is what you want it to be - maybe you don't need anything.
A good rule of thumb to follow in priority is:
1) The best recording medium you can afford - which meets your needs (number of tracks, portable, etc. ect)
2) The cleanest signal path into your recording medium
3) The cleanest path out of your recording medium - to what ever two track format you choose (in your case CD)
4) The best (most accurate) monitoring system your can afford
So in your case, does the MR8 provide a clean signal path? Are you satisfied (for now) with your mic'd signals? Are you getting a clean recording to the CD? Are your monitors allowing you to get a mixdown that translates well to other soeaker systems (not too bass heavy, etc).
Once your figure out what you don't like, then maybe someone can recommend a solution.