Which Would You Choose?

What specific improvements are you looking for over the JC5?  Also, I’d consider upgrading the Monster 3600 that can’t be doing you any favors sonically.

@soix 

+1

Naturally, upgrades in components should yield improvements in sound. This is a complex subject. I could go on forever. Before you go that route, I would suggest improvements in all of your cabling. There are currently several high-tech sources that have "finally" discovered the sonic benefits of using 7n's OCC solid core copper wire, with silver plating, as the main ingredient in all of the cables offered, Including highly shielded power cord construction. Personally, I use custom made cables utilizing this material and construction, however I have recently come across a manufactured source that I would buy in a heartbeat if I didn't already have what I have. I suggest contacting DECAWARE in E.PEORIA, IL. Talk to STEVE DECERT about all of his current OCC cable designs. This person is truly an audio design genius, so you can ask him anything. BE CAREFUL though !! "All of his component designs are incredibly addicting, including speakers. His company is one of those hidden gems in the HIGH END audio business.

You speakers are in an entirely different class to the rest of your equipment and you probably need to think of upgrading almost everything not just a power amp.  Actually IMHO your power amp is the last thing you need to replace.

Your room