Looking for advice on speaker cables for proac d38 and arc ref 150

i was assuming that what worked well with ss marsh might not be an ideal match do to change in impedance .  

narunner2,

You have a great system. As has been said your MITs are some great cabling but if you find that you'd like to try something new I would recommend WireWorld Eclipse 7 or Equinox 7 interconnects and speaker cable. 

Cheers,

Scott

In the 90's when I was using a full Goldmund system with Proac Response 5, the best speaker cable hands down, way above MIT, Transparent, Nordost, Siltech, Tara Labs, was the Cardas Hexlink Golden 5C. The difference was huge! Later versions like Golden Cross, SE9, Golden REF, were not to my liking. I can't comment any further as I don't know about ARC amps, but I can tell you that Response 5 has Belden inside. Till today the most capable speaker cable  known to me, is the "Physic Harmonic ECO" handmade by Andreas Pollakis (Facebook).
The price is low  but the outcome is so great, you must witness by yourself. He gives 30 days money back guarantee so, you don't have much to loose. (To test it is to keep it. Always!)
Good Luck

Agree with the WW recommendation.  Also, Audioquest and Cardas.  Best....

I have Proac D-30R's and I'm using Clear Day Cables. I have used
them with both tubes (Manley Snappers) and now SS (Pass X30.8).
I would recommend you contact Paul at Clear Day cables and demo
his cables. It will cost you next to nothing and you can see if they fit the bill for your system.