ScienceOne, If you're not sure, than you might not need one. I'm really not qualified to give advice; I'm just echoing the views that were posted to me.
I thought I needed one, especially according to the salesman at Guitar Center. When I got the DMP3 and the RNC compressor as a lot of guys here suggested, (in my price range), I experimented.
I found that I got really surprising track quality. That is the bottom line I guess. The few spots that the limiter/gate may have helped on I scrubbed out. I ended up returning the composer that’s not to say that you may not need it. I record one track at a time also.
One thing that someone here told me that I can really grasp onto was " the less stuff between the mic and recorder is a good rule of thumb." I'm sure the lower the price range of equipment that we're in would just amplify that rule.