I went from and all Reference system to changing my XLR interconnect to Reference XL. Leaving the speaker cable at the Reference level. There was a positive change for the better. It's been long while ago, but i think the bass was much better. Did i get the full benefit of the Reference XL, chances no.
I'm sure you will get better sound with just the change to Opus speaker cables. Will it be worth the cost? Only you can make that call. Speaker cables changed to Opus today interconnects change to Opus down the road, Would be what i would do.