Looking for ideas - new mono blocks for stereo music

Interesting system you have.  The Marantz receivers are actually pretty good. I use a 7702 Mk 2 pre in my AV system (the one that superseded it was a step down) and as I use two different amplification set ups depending on whether I am doing AV or just pure audio, I sometimes get lazy and leave the AV stuff (all solid state vs. the 'listening system which is tube) in the loop when I want to do a bit of casual listening and it is very decent.  BTW, think about going to a separate server with all your music on it - I have around 4,000 CDs and for the first time I can actually find anything I want on my computer when I want to play it!

I haven't heard your power amp but have found several of the Bryston power amps a tad dry (I do run one of their preamps, a BP17, in a second system, and have an old 2B power amp - still a pretty good sounding unit despite the age, in my library system).  I don't know that you need monoblock amps and can save some money by going for one stereo amp and as I am also in Canada, I think the Simaudio products are a good way to start looking, but don't discount the early Dave Reich designed Classe amps - they are once again up and running under new ownership and I was able to get one of my old Classe DR3 - VHCs overhauled with no problems.

There are a lot of heritage older amps out there that compare well with current stuff.  I run an older Roland in the AV system, for instance and you can buy them for a fraction of what a new amp costs.

I’ve enjoyed the Krell 575 monoblocks for 6 months. Not a day goes by that I am not thoroughly happy with them. No problems with heat. 

Another vote to consider the bhk 300. Been lusting for them. Luckily they arrive next week, going to be a momumental upgrade

using ampzilla 2000 2nd edition monoblocks & very happy with them.  300 watts into 8Ω & 540 watts into 4Ω.  no issues with heat.

https://www.sst.audio/ampzilla-1/

Hi eothar,

I am Joining this discussion late, but if your still checking in I would concur with those who say that your issues would lay more with your power delivery. Your amps, 600W@8 ohms, have twice the rated power necessary to run your speakers. Your amps are not being maximized to their fullest potential - they are not getting enough power. If you have 20K to spend look towards Cabling. 

Also your JBLs have a frequency response of 32hz -40khz, you may want to consider adding a pair of subs. I had a pair of speakers with the same frequency response. I adjusted my power cables and added a pair of subs which gave me the desired effect you are looking to achieve.

My suggestion for getting the best value added out of $20K
Start by adding these cables, which would be better than adding  power amp to your system.

Stage 3 Concepts - will open up the soundstage and resolution - provide clean detailed bass and spacial separation you are craving - Think Krakens. 
www.stage3concepts.com

HB Power distributor - Power Slave....
www.hb-cable-design.com

Thales - for the price the best speaker cables you will ever own will add the detail you are seeking
www.tonarm.ch

I looked to REL for my sub Issues. JL makes great products as well - look for ones with at least a 15" drivers to pair with your JBLs. 

What I have realized is that most Speakers that have Frequency responses that run below 21 hz are usually have active subs.
The few that are not are astronomically high priced, except Devore's
Silverbacks - discontinued.

Good Luck