Worth upgrading from Morrow MA4's?

I doubt it.....

While I'm not familiar with your sources, I am familiar with your pre-amplifier, amplifier and speakers.
IF your system is well set up to recreate the recording as it was performed, than without a doubt, your system will perform better with better cables.
I'm a dealer, so I can't recommend what cable I found best (and why I became a dealer for that cable) - but I can state with absolute certainty that your components will sound better with better cables.
Only good wishes, TJF.

Upgrade to Putist Venustas Luminist wonderful musical great dynamics etc

Rrolack - Doubt anyone can predict with certainty whether MA6s or 7s will provide you with a meaningful improvement (barring the unlikely event someone has your exact gear and listening space and has tried). Pretty sure Morrow has a trade in/trade up program as well as in-home trial. I suggest you email or call and see if these can work together...get a trial on 6s or 7s with option to return if no improvement or credit for trade in of your current MA cable if you keep the 6s/7s. In my experience (MA3 ICs from pre to mono blocks; SP4 from integrated amp to speakers) Morrow is very customer-friendly and will work with you - so definitely worth a call (or email) to them.

A point to keep in mind regarding analog interconnections (I presume you are not using an MA4 for the digital interconnection), is that the longer the length of the cable the greater the difference the cable is likely to make. Also, higher output impedance of the component which drives a cable will tend to increase sensitivity to cable differences. Your preamp has a considerably higher output impedance than your DAC.

Also, everything else being equal balanced interconnections (which I presume are what you are using) will generally tend to have less sensitivity to cable differences than unbalanced interconnections, especially when driven from a low output impedance.

Good luck. Regards,
-- Al