If you liked the KX, you might enjoy something like a KLX140 or a Yamaha TT-R230. Both are solid, reliable bikes and great for casual trail riding. Really depends on what kind of riding you plan to do next.
Welcome! Not sure what a KX20 is, but before you can get a recommendation, we would need to know a few things. Riding location, style of riding you do, skill level, etc.