Replace au24 speaker cable???

I have for years used the au24 speaker cable with my dartzeel preamp, dartzeel amp, and evolution acoustic mm2 speakers with powered woofer

The au-24 is well balanced and cannot imagine much more bass slamm but maybe more midrange?

System sounds great but maybe this is weakest link. The ic cables are bnc connectors which is optimal for dartzeel equipment.

A friend brought his kubala to try but I found the kubala too dark

The stereovox silver reference seems tempting but not sure if worth the $ and limited budget

well, it's hard to imagine a person with the equipment you've listed being on a "limited budget". perhaps you could contact and try out several different brands of cables to find that works best in your system. have you tried you the zeel interconnects? also, evolution acoustics makes their own line of cables as well.
Try to demo the Jps Superconductor 3's. I just demoed them and was very impressed. I personally never heard the AU24's but the dealer who let me demo the Jps and is also is a retailer for the AU24's (not local) say's the Jps is no comparison. He also mentioned they are very similar to the Synergistic Research Apex.
I went from Au24 to Empirical Design cables and gained noticeable improvement across the board. The ED cables were both more detailed and more natural sounding, particularly through the midrange. It is also an excellent company to do business with, offering custom lengths, terminations, etc. Karl knows what he is doing--no smoke and mirrors BS.
I am using the zeel bnc interconnects

I say limited budget because spent most of the budget
On the components

I also believe that the speaker cable should be neutral and not act as a filter or equilizer so why then should costs thousands
I've used Acoustic Zen Satori's in my system for several years, but I recently tried the new "e" series Au24's out of curiousity and, frankly, was underwhelmed. Great bass, as you indicate, but the midrange and treble presentation of the Satori's was much better in my system. YMMV, of course.
Xti16 says that while he demoed the JPS Superconductor 3, he "...never heard the AU24s..." I demoed the AU24e speaker cables, considered to be an upgrade of the 24s, at the same time I demoed the Superconductor 3s. IME and IMS, the latter bested the former in nearly every category. I recommend you take the opportunity to have The Cable Company send you both for your own evaluation.
I'm a dealer for Evolution Acoustics and Dartzeel. I'm running the same components. I'm using the Evolution Acoustics double run speaker cables. They were far superior to my previous reference cables which were pretty spectacular. I was over a customers house with the same system and the Evolution cables handily outperformed his reference cables that were far more expensive.
I had Au24's and just changed to Stealth Hybrid MLT and was very pleased with the improvements. It provided greater detail/quieter background yet sounded more relaxed with a larger soundstage. A friend of mine commented that it sounded fuller/richer sounding but more detailed. It is not dark at all but it is also not bright, very neutral actually. Very natural sounding and I would highly recommend them.
Well, I too have just upgraded beyond the AU24 speaker cables. (Seems like a lot of us have upgraded from them recently.) Before I state what I moved up to, I should state that I believe the AU24 speaker cables are very good speaker cables, especially for the money. (i.e. a very good bang for the buck!)

That being said, I have moved on up to the Jena Labs Pathfinder speaker cables (bi-wired). This cable seems to have better detail and resolution, and is slightly better in the treble response especially. I like them a lot. (Of course I should for twice the price though!)

My two cents worth.
i am a bit puzzled by the comments so far regarding the au 24 speaker cables.

i had an opportunity to audition the ics, power cables and speaker cable.

the au 24 was not lacking in resolution. in fact i found them somewhat analytical and too focused for my taste. in addition, i did not find the bass response more extended or having greater impact than other speaker cables.
I had Au79's before going to Synergistic Research Tesla. In my system the Tesla Accelerators were more resolved, threw a much larger soundstage, and had a more textured and musical balance.

I suggest you try cables from different manufactures- in addition to SR Tesla I would also try cables from AQ, Cardas, and Nordost. That should cover the neighborhood pretty well.
Reviewing and auditioning is much different than living with them day after day. I think people change cables almost on a routine basis to get something different but over time tire of them as well....and around and around we go.