Considering switching to XLR cables,

I have an Audio Research Reference 6 preamp, I used to have a Pass x350 amp... and my speakers used to be Apogee ribbons.

When I got my new Audio Research equipment (Preamp, DAC... and before amp) I had Transparent single ended interconnects (after choosing from half a dozen brands). So I bought a single Transparent balanced pair of interconnects and compared them. I couldn’t tell the difference. I attributed this to Audio Research putting the R&D time into converting to single ended from the internal component topology) I did not spend a couple weeks carefully listening... it was a fairly quick comparison. But any difference was small. I am sure if I spent a couple weeks I could find some subtle differences. But typically XLR can be up to twice as expensive. I finally replaced them all with XLR just to be safe... since the audio world is going that way. If I couldn’t have afforded it I would put a premium on the quality of the interconnect over the kind of connection. 

On the brand. I recommend Transparent. They are exactly that. For Audio Research and Pass equipment that is what you want. I don’t know of any brand as neutral and quiet. I have tried many. If your equipment isn’t up for them then that can be a problem. But your ARC and Pass is. Transparent has decades of research and each generation has achieved better and more transparent / reduction in noise. This is why for instance, there is a known synergy between Sonus Faber, Audio Research, and Transparent.  

What specific improvements are you looking for?  Without that critical info this is just a total crapshoot. 

Don't toss your RCA's. Sometimes and in certain positions lower voltage is called for.

Honestly I don’t think you’re going to hear a difference between RCA’s or balanced other than the fact that the balance are going to sound a bit louder without increasing the volume. If you were going to try balanced, I would recommend from the selections you listed above the following;

 Zavfino Arcadia

I'll echo what others have said, it really depends on your gear and how it is implemented. I don't think XLR is inherently better than RCA in most cases. Unless you need a really long cable run which is where XLR is clearly better. But most people don't need anything like that.

You need to know if your DAC is truly balanced or not, and same with your preamp. Otherwise there is conversion involved which can be done well or poorly depending on the design. 

I've been enjoying the Veritas Cables Argentum R for a while, which is a silver RCA design. Recently I picked up the Argentum X which they say is a very similar design but in balanced form. In one of my systems I can't tell the difference when I switch between them. But in a different headphone based setup the XLR interconnects are much more enjoyable. I don't think that is related to this particular cable design, it's just that the DAC and headphone amp do best when operated fully balanced. 

If you do decide to try out a set of XLRs, make sure to buy something you can return if you don't like or hear a big enough improvement. I can vouch for Triode having a good policy like that, not sure about the others you mentioned.