Ideal set up:
Batt-fuse-Cap-amp (1 line per amp, all 0AWG or 4AWG)

Practical set up:
Batt-fuse-distribution block (0AWG up to here)-cap (1cap per amp)-amp (4AWG)

As for the sub, 1100W is peak. You need to find out how many watts RMS (aka nominal W), then get an amp that will provide more than that (also in watts RMS). Damn heavy means nothing nowadays, cause of new magnet materials.

Sincy
How bout this budget solution:

Your current front speakers put in the rear and run by your HU directly. (actually better to remove it completely and sell)
You buy decent rm700 component speakers for your front. (macrom, peerless, focal, diamond)
Your 4ch amp: 2ch ---> front component speakers
2ch ---> subwoofer
No need buy monoblock, no need add new power cables.

Other suggestions:
sub alternatives----> 2nd hand Rockford Fosgate P1 & P2 for >rm300 including box
----> Alpine Type S shouldn't be more than rm400
----> Pioneer/ Blaupunkt subs should be miles better than any chicken chop stuff you can find

4AWG power cables through out your system will serve you well for many years.
Prices of China RCA and power cables are very close to entry level decent branded ones like Stinger, Directed, Audison, Streetwires. Do consider them.

Out of the 2, Pioneer definitely. But that model, eh....... isnt it an old model? If the price is around 1k, better go for Pioneer 8000 or 7000 series. Or Alpine 9887 2nd hand.

Ya 4gage ok liaw. I still think you should get better component speakers for your front and put your old 1s behind. But up to you la. Slow slow......