Looking to replace Acoustic Zen Matrix Reference

Looking for something new with more extension top to bottom at a reasonable price. Currently have the AZ single ended between Joule Electra preamp and Bryston Amp. Less than $300 on the used market.
Not a cable expert but if you're looking for more extension on top and on bottom I don't think you will find much difference at your price point. In my system which has useable response below 20Hz and has a ribbon tweeter, I don't find the AZ ICs a limiting factor in that way. They may be a little on the warm side of neutral if you want to change the tonal balance. To tip the balance up go to the AZ Silver Ref IIs. You might try moving the speakers around and toe in aiming them more towards you. That will have a much greater impact than cables at the frequency extremes and is well within your budget!
Thanks Barry, you have a great setup...
Silver/teflon, e.g., AZ Silver Ref II or DH Labs Silver Revelation.
I used to own AZ cabling and eventually went with all Nordost. Nordost really worked well in my system. The Norse 1 Frey's or Heimdalls are in your price range used. I personally own the Frey's in my system and love them.
I'm glad that your speakers are getting into the groove. If you're looking for more extension on both sides, even though at twice the budget, I think you'd have a hard time trying to find something better than Clarity Audio cables. Will help with the focus which omnidirectionals need typically. There's some for sale right now.
I have several versions of Matrix Reference and Silver Reference ICs around, and in my system the Silver Refs are more revealing up top (i.e. more air and better-defined highs in general with more transient snap as well) without crossing over into brightness or harshness. This is especially true of the original Matrix Refs vs. any of the Silver Refs. The Silver Refs also yield tighter and quicker bass. I didn't care for the Matrix Ref IIs, which were a little glaring to my ears and lacked some of the fullness/warmth of the original. I think the original Silver Refs come pretty close to the Silver Ref IIs, so if they better fit your budget it's not too much of a compromise (although go for the SR IIs if you can swing it). Considering what you're looking to improve I'd think the Silver Refs would be well worth a try. Best of luck.
Soix, you reminded me that I have "Matrix Reference II's, not the originals, thanks.