Would my system benefit from cable upgrades?

To answer your question yes the cables will make a difference. But a better path would be to sell the motion 40 then add your $2k-$3k to buy a better pair of speakers. Shop the used market.
 

if you’re really itching to upgrade cables you can try and replace your generic interconnects with something like the BlueJeans or the Mogami Gold with whatever is left of your budget. Just my take on it. 
 

Once again: 

     NO ONE can tell you whether/how your system, room and/or ears will respond to new/improved interconnects.   There are simply too many variables.

     The only way you’ll know for certain, is try them for yourself.

     The least expensive way: contact the guys at The Cable Company and take advantage of their lending library.

     For a pittance, you can try a few of their offerings and the rental fees are applied to any purchase made.

     In you shoes: I’d try the three Audience Ohno cables, currently available (RCAs/url below), between your TT, DAC, SACD player and Vincent.   With new/improved cables, in those critical positions: you should easily gain the knowledge you seek, one way or the other.    Even with your current speakers.

                   Whether to explore/spend further: up to you!

                    https://www.usedcable.com/audience_.html

                    https://www.thecableco.com/lending-library

Read this first. Then decide.

I think quality cables that are reasonably priced are the route to go.

As others have stated your room is a huge factor. You will net better results than spending $$$$$ on copper and silver and...

@mesch and @jjss49 are right.

More insight.

Your amp MIGHT benefit from a power cord upgrade....I believe something larger than 14 Ga. As for speaker cables, what you have should be fine. There's a reason they've been around forever. There is SO much marketing BS around cables. Don't fall for it.