Any cable delivers more bass than Cardas Golden Reference?

I've owned Merlin VSM for years, I agree they can be somewhat lean. I'm not sure you can do better than Cardas GR with these speakers. I've used, Kimber Bifocal XL's and Purist Audio Design Dominus on other speakers, both have a prominent bass.
I've found mods to both speakers and BAM to have a positive effect. BAM mods include Duelund VSF, Texas Components naked vishay resistors, larger capacity power supply caps-Nichicon Muse 220uf 100v, discrete power supply regulators, EBL 600mah batteries. These mods gave a much fuller, natural, unforced sound, greater transparency and resolution added bonus. Short of all mods, the Nichicon Muse, Duelund caps and batteries will effect bass most greatly. The larger capacity Muse will require a larger enclosure. I also use the Duelund VSF in speaker crossover board.
Short of mods, I've found a sympathetic amp, 845 SET's are perfect for the Merlins in my estimation. Full bass and enough power for the moderately efficient Merlins.  Sympathetic front end components can also help with bass. Certain power cords with your amp could also be helpful.

Got a vintage set of Monster Cable....1986.  Think I payed $30 for them.....the bass on my DQ 10's is fantastic.....and they're probably burned in by now. ;-)

https://www.youtube.com/watch?v=UoVixorZTDM

Watch it till the end...

Another recommendation for Purist Audio Design Dominus.Over the years I've tried many cables, several in the Purist line and of those I've tried, Dominus Luminist is my top pick for very natural, lightning fast, full bodied bass.  It was so striking to my ear (and emotional impact to my body) that it seemed like I'd gotten my electronics to reach deeper and more natural.  I fact, so much so, my whole loom is now Dominus Luminist.  Taken some time and $, but I am a happy camper and still discovering things in the mid and deep bass I'd never heard before.  (Oh, and the clear attack, schimmer and decay on jazz cymbals . . .)  My ears and the way my brain decodes audio waves have experienced nothing better.

Footnote: Since every set of ears and sound wave decoding brain, set of components, room and personal preference is different, results and opoinions will vary from person to person.  Your experience is foremost.  Unless you are very familiar with the sound prodced by a lot of component and room configurations, new anything has to be tried in your system in your room.  There is no best!  Only preferences and opions, mine based on my experience and still only based on my preferences.  Only yours really counts.  Good luck.