@TLS Guy  Yes that might be  reason.  To get the best movie and gaming experience I  listen rather loud to   real ht experience.
Looking into a good amp is great idea. Thanks for your recommending the quaad 606.
@lovinthehd   The speakers are on the left and right side of the TV. The seating distance between me and the TV Chair is about 3.5 meter.  In order to get good home theater experience I listen  I crank up the volume.
Getting a subwoofer to reduce the strain sounds like a good idea. The purchase of a subwoofer is planned anyway.
At some point this year I  plan to get  XTZ sub or the svs pb 1000pro.
@all So  you think it would be good strategy to try to get good amp  first before getting rid of the onkyo? In case this not working  the  amp would still be a valid investion.
I can use the amp  as well with a denon x3800 or the Yamaha .
is the asumption correct?