I had to drill a hole through it to get mine through, I'm pretty sure that is the only way. I have no clue on the RCA mine just hooked up to the head unit, but I have no aftermarket speakers.
Most aftermarket stereos with only two sets of RCA out have the option to set the rear channel to sub output or full range speakers. You should be able to set it to sub out and then split the front channel RCAs to run front and back speakers. You will lose the fade control doing this but it's going the easiest way.
Get on amazon. and find a Cable Gland to fit your wire, and drill to match. The power can go driver's side to the battery, or pass side, to the starter. I run rca's and power on opposite sides. Put a fuseholder at the battery, so you don't set the carpet on fire.
I've had customers not do that, and stretching the wire the last inch set the carpet ablaze. Nothing burns like a 10 awg wire, across a 800A battery, lol.
On the sub, if you dont have a sub out , you need a crossover.
Since you have a 97 there’s an unused grommet on the passenger firewall you could easily run cable through, I did my battery relocation through it previously and currently use it to power my gauges as well as my JBL sub amp. You can run it off the battery terminal on the starter under the frame rail and up through that grommet to keep it out of the way of exhaust and other engine entanglements