in-wall speaker cable help

I use Analysis Plus Blue Oval for the rear speakers, and I'm very satisfied with them.

Unfortunately the system placement must remain as is. There is a little bit of slack right now, so I could probably reduce the length by about 4 feet or so.

At present I am using Monster speaker cables which were supplied by the installer who was not an audiophile. It is 10 or 12 gauge. Unfortunately, at the time I was too busy to specify what type of cable I wanted so the installer did the best he could. The system sounds very nice as is (with no noise, and very musical). Now I have an opportunity to install a new run of speaker cables due to some new renovation that needs to be done.

CL3 rated cable is shielded to avoid interference. I have been researching Kimber Quick 12, Analysis Plus Blue Oval and Transparent (they have a few products for in wall applications).

Any feedback or recommendations would be appreciated.

Many thanks.

50 feet is quite far for interconnects. I'd bet on it that you get noise and signal loss. Don't do it!