I don't know that you'll find the BEST boat for Cumberland River/Dix River is the BEST boat for Lake Cumberland/Lake Herrington.

If I were going to run Cumberland River, Dix River, etc...I'd get tunnel hull (one that's designed for a jet) with a jet drive...a planing style hull, that's designed for shallow water applications. For the lakes, that's probably not what you want though.

www.jamesriverjets.com

www.rockproofboats.com

www.www.riverpro-boats.com

www.snyderboats.com

On that Snyder site, check out the FAQ section...a lot of good info about jet boats there.