This is the next big step for me - will I invest on the power supply side. Any advice on the lowest cost strep in this direction which will then demonstrably build my confidence to go for the big one!
The best low cost step is to slowly back away from the beast while you still have your sanity and a little money in the bank Once you step thru the door there is no turning back.
It’s like a horror movie. “Are you crazy? Don’t go in there!!!”
Just grab an HDPLEX 300. It is four LPS in one and still less than a souped up Farad. One supply at a time is incremental all at once is a games changer. LPS matters at every link in the chain and improvements are additive especially if your cables are up to it. But that is another rabbit hole that swallows !
I’d go speaker first. Your Roksan gear is pretty darn good.
A power source is also a good idea, and I’d agree with the people who suggest speaker, power regen, and then amps. With amps, I’d probably stick with the M700s and look to upgrade your source next - likely a DAC (even if your Cambridge is pretty good).