How to hookup a 4 Channel amp to a stock radio

Hello, I have a 2012 ml350. I want to install a 4 channel amp to my car because I want more sound. I do know that mercades already have amplifiers in them but I want more. I don't know if many of you know what a chuchero is but I want to install one of those into my car. So basically I have a 12 inch 900 watt audio pipe bass and I orderd 2 audio pipe 8 inch speakers which are 500 watts RMS each. And a tweeter & a driver. I'm thinking on buying a 2000 watt 4 channel amp but I'm thinking it won't be enough power. "Audiopipe 2000-Watt 4-Channel Amp" to sum this up I know it's a little bit long but I just want to know how can I get the rcas with the high low converters? Do I need two high low converters or do I only need one? I also have another question. If I tap Into the rear speakers for one high low converter( for the bass) can I just tap into the front speakers for the mids? Or does it not work like that. I just need a professional to help me out because I'm stuck and I don't know what to do. Thanks in advance