hmmm..
I suspect what you experienced with Ls50s is inadequate power , creek 50a will do well with mid size floor standers and anything with high sensitivity.
Havent heard the gx100 but had the Rx6 for a while , the monitor audio sound wasnt for me ,then again it comes down to personal preference .
You mentioned not enough bass , did it lack depth or punch?
happy listening and cheers!