Edit: ugh just realised I posted in the wrong section.
I want to run my speakers off one amp and a mono block for the sub. Has anyone had any issues with this kind of set up ? I tried the same set up in a newer 2000s car with a whole ton of other electrical stuff and the speakers would cut in and out when driving, ended up taking the amp out for the speakers and just ran them through the stereo and all good. Just don't want to do all the install work on the TA and have the same issue so any info is much appreciated.

 

The problem won't be "the battery"; it'll be "the car electrical system".

Alternator, charging wire, batt cables, power supply wiring (including grounding) to the electronics. All of that has to be able to deliver the power the amp tries to draw. In theory, shouldn't even matter whether there's a battery in the car or not, for the purpose at hand. The car's electrical system must be able to sustainably deliver the current that is required, at a voltage (minimal voltage drop in the wiring due to resistance due to it being too small) that the electronics will be happy with.

Won't too much matter whether anyone else has "had issues", although I can ASSURE you that they have; all that matters is how YOU build YOUR system.