how much more are you willing to spend?

if you have enough budget, i would say get a 4 channel amp with enough watts

2 channel for component sets
another 2 channel bridge to mono, to power your subs

for rear speaker, you can just wire direct from the head unit

your old amp just lelong cheap cheap .... nothing much u can do with 250w pmpo

Firstly, the Brother guy who said 4-channel plays more sound is bullshit, or rather interpret the channels in the wrong way.

If you read my previous reply properly, I never mentioned about using 3 amplifiers at once.

I recommend using only one 4-channel amp (with sufficient watts of course). Since it has four channels, you can use two channels for the front component speakers. Another two channels can be bridged to mono and use it to power your single subwoofer.

For your car rear speakers, it is better just connect it direct to the head unit. Rear speakers are best to keep low so that it does not interfere with your front components.