Would I be able to just swap out the stock amp in the trunk w/o having to rewire throughout the entire car?

I currently have the Bavsound speakers + ghost subs, but it just isn't enough. Lacking mid-bass....and just bass in general. I was hoping it would be a relatively easy swap to change from the stock amp over to a 5-6 channel amp? Suggestions are welcome.

 

a little update:
I've been going back/forth on what I can do (with the least amount of work wiring)....and ordered a 2-channel amp to power the Bavsound ghost subwoofers under the front seats....leaving the 4 Bavsound speakers in the door powered by the headunit. I'm hoping this will hold me over for a bit since I feel the ghost subs are severely underpowered.

I spoke to a Bavsound rep yesterday (Jeremy), and he provided the specs on how much the ghost subs can handle (~50w @ 4ohms), so I purchased a cheap JBL 2-channel amp that falls within these specs.

I guess the question I have is how to minimize the wiring for these 2 subs & amp. I have plans on cutting off the connection that goes into the ghost speakers and wiring that directly to the amp, running power directly from the battery using fuse line down one of the door sills + also tapping into the rear cigarette lighter for remote tap? I'll be using an 8 gauge amp wiring kit, but curious to see how others have wired an amp like this with similar setup...

 

also does anyone know of any other harness tap I can use so I wouldn't have to cut the subwoofer connectors off? Technicpnp sells a 2/4 harness @ $75, but I wouldn't need that entire kit....just need the connectors for the ghost subs.