Speaker cables to smoothen things up

I love the sound of my system. Its dynamic and neutral and very lively. However, my taste to music have melowed somewhat, and im prefer a smooth, relaxing sound at the moment and was wondering if a speaker cable change would smooth things up somewhat and reduce the hardness and attack from my system ( not bright, just hard)
My speaker cables at the moment are some synergistic research tesla quad. I got this for free from my brother therefore ive not tested other speaker cables.
Interconnects are tchernov reference cables and my subwoofer inteconnects are fat oval ic.

The chain goes as follow
Mac mini with audirvana - nad m51 - densen b200 -densen b330 - neat ultimatum mf5 and genesis g928 sub.

Was wondering if a speaker cable change would smoothen things up. Its not to reduce the brightness of my system, my system is pretty neutral. Just want to reduce some of the attack and dynamic off the system. If possible, not wanting to change the amp and speakers.

Ive heard about van denhuls to do this, and ive got a good deal for a d352 hybrid cables. Also a good deal for a kimber 8tc ( the older black and blue version). Would these help? Any reccomendations is much appreciated

Just for info, my room is almost fully treated. Big drapes and rugs and diffusers and bass traps all over.
I'd suspect you are expecting too much from a speaker cable change. In my experience, they affect the sound of your system less than interconnects and power cables. If your listening is all via the mac mini, have you considered implementing digital equalization? If my computer was my only listening source, I would implement this approach without a doubt. http://www.spatialcomputer.com/page3/page3.html
acoustic damping and other room treatments can bring you more successfull and even more econonic results vs. experimenting with cables.
cardas cables are smooth and extreme warm.
Since you have Synergistic speaker cables why not try another product of theirs XOT transducers. You can try them for free for 2 weeks. You get a full refund if they do not do the trick. Easy to install and remove. Cheaper than a lot of new cables-$399.00.
Good luck Pete
+ 1 with PHOTON46

The takeaway: system synergy matters ....big-time ( an alchemy of the electronics paired up with cables (power/IC/speaker) and with your speakers)

In this context:

(1) consider re-evaluating your source as the first step in cutting out the "hardness"
(2) revaluate the system synergy as a whole: it may be more than just a non-optimal fit with the speaker cables alone.
(3) budgets matter .... sure .... but there is also an inescapable truism in this hobby: you get what you pay for. IMO with the Densen kit and Neat speakers, I would look at the LFD hybrid speaker cables and LFD ICs. (I personally demoed a dealer system with DENSEN/NAIM/ NEAT/LFD mix and match alternatives)

Google them : I believe Gene Rubin Audio carries them

w/o prejudice to the former, I've had the VDH d352 hybrids with very mixed results. I sold them: these worked "meh? to Okay" in my experiences with lower rung kit like NAD (had them hooked up to a NAD kit in a prior "B" system); but quality gear like your DENSEN and NEAT crave much better quality cables to perform.
They did not perform to my expectations in my hi-end A system and were smoked by the NORDOST FREYs. The difference was not subtle.

You have to go way higher in the VDH chain to get quality performance in your system IMO.
Cardas or Tara Labs.
Yes to room treatments which can amount to equalization.
If you want to try changing cables, call the Cable Company and use their
lending library. Tell them your requirements and they will advise you.

I have found that Cardas ICs will make a system more laid back, but IMO
their speaker cables colour the sound.
Spatial Audio Quantum Field speaker cables and/or pair of their VB1's should do the trick.
I've heard Densen and Neat stuff and it's not laid back at all :)

8TC is clean/neutral/not warm so I'd rule those out.

Van Den Hul is pretty laid back but I'd trust their ICs over their speaker cables; can get quite pricey for what it is (in the US at least).

You might like to try OCC speaker cables in the vein of Neotech, Audio Sensibility, Acoustic Zen, depending on your budget.
Cardas Golden Cross, or probably any of the older Cardas cables like Neutral Reference will soften things up for sure.
Cables won't do it because they cannot overcome the fundamental sound that your components' circuits have. Sound lies in circuit and speaker design, not cables.
Antipodes cables.
Nieveulv, I reread your post and if your system is too dynamic and "hard," then changing cables won't do much for you. Cables can be used to change the timbre or affect the soundstaging, but not to change the PRAT of a system.

So I'll agree with those who say a change in source or component is in order. Not familiar with your components, but as you know it's all about system synergy. Bojack has hit the nail on the head.
I don't have much experience with speaker cable experimentation but I've tried numerous interconnects and power cords over the last few years. My system was very dynamic with a pair of Fusion Audio Enchanter power cords and a Virtual Dynamics Platinum Nite pc. The interconnect was a Granite Audio 470. Speaker cables were DIY copper wires from Polar Cables. Dynamics could be absolutely jarring. I wasn't quite satisfied though with the precision of image outlines and there was a slight bit of midrange brightness so I worked some other cables into the mix. I found the Sonoran Audio Plateau interconnects to soften things up a bit, reducing bass slam well into the lower midrange and a pair of 6Sons Audio Windigo power cords improved imaging and detail while softening dynamics. This wasn't what I was looking for but it may well help you. Good luck.
Agree on Cardas...would also suggest for the money to try some older Transp Reference cables...you can find them here for cents on the dollar. I would go back to 10 year old cable...the reference level or above. There was Reference, Reference XL to start with. Very smooth, dark backgrounds...in fact some say they were designed when the original Wilson X1 series was still around...and being quite scientific in the treble, the combination with Transp Ref worked quite well.
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Before you buy new speaker cables, make sure that your cables are properly dressed. I.E. make sure that interconnects and speaker cables are not run parallel to power cables. If they must run parallel, get as much distance between them as you can manage. If they cross each other, do so at 90 degree angles or as close to that as possible. I realize that many audiophiles understand this, but most certainly some do not. It can make a substantial difference in the amount of noise/hash in your system. It can manifest itself as harshness when listening. The best things about this is it's easy to do and free. Hope this helps.