I have a Jeep wrangler and need stereo I can hear but it doesn't have high end, just loud enough.

I had a 4 channel amp under the seat and worked great for about 10 years and finally died.

I want an amp that fits where the head unit goes and I want to plug my smart phone into the amp and no head unit. I want it out of the way and better protected. I am running 4 speakers and a sub. I spliced the front and year speakers together right font and rear and left front and year and bridged the sub.

Space is limited in a Wrangler and I don't want another big amp taking up floor space.

any recommendations?