Questions about amps

[DrEvil]

Looking for some help from you knowledgeable folk!

I have a B7 rear amplified system. Now fed off an aftermarket HU but needed to use a HiLo from the HU direct speaker outs rather than the pre-amps HU outs. System is feeling low on base and a bit tinny.

So, was thinking need a sub or something, but maybe the first thing I need to do is to get the best out of my existing speakers. I don't really want to be running lots of wires (but could do some of this) and really don't want to be pulling open door cards (don't have the time to do that) and don't want to spend a fortune on this at all (will be looking for second hand equipment).

Will adding an amp to my fronts largely solve my issues - or a 4 channel amp and using that instead of my existing amp?

 

[DrEvil]

As a follow on question, been thinking about an amp.

If I was doing a 4 channel amp, the best place for a hidden location in the boot panel (avant) where the existing amp is. If I did want to place a 4 channel amp here, would I need to run 4x RCAs from the pre-amp outs of the HU to the low level inputs from the amp, then from the speaker outs, I could try and hook into the existing connector in the boot to wire up the rears, but I'd need to run cabling back to the HU to wire in the fronts. I could also use the power and amp on etc from the existing connector.
Is that the best way of wiring it up?
Is there any easy way to tap into the connector in the boot without having to cut it all up?
Whats the best way of running the wires?

Trying to understand the DIY hassle factor of it compared to maybe looking for a 2 channel amp in the glovebox to power the fronts and then a device to help out the rear amp?