Hi Darren,
It kind of comes down to why the sell through rate is low and that can be many factors. Maybe it's a simple as the price being too high, maybe bad keywords not bringing in enough traffic and so on. The only way to really get a good idea is to take a look at the competition, see what they are doing and see if you can do better.
If you can identify some weaknesses that you think could be slowing their sales, then it's well worth doing some market research by trying a few listings of your own.