Speaker or amplifer

I tell you that I like it so much that is the only Hi fi equipment that I have not sold. I have the older model that has the gelco 9” arm.

What sub are you using?  It’s a little curious that you’re lacking slam while using a sub assuming it’s properly set up. 

I’m using Rel T7i subwoofer.

That explains a lot. The REL has an 8” driver and only goes down to 30Hz at -6dB so is more like a woofer than a subwoofer, which explains why you’re not getting much slam. All you probably need is something like a Rhythmik F12G to get you what you’re missing.

https://www.rythmikaudio.com/F12G.html

If a Hegel demo is available I really do not understand what the problem is. 
Demo the damn amp.