6 channel setup

I would like to setup my vehicle 1986 Merc 190E 2.3 with a 6 channel amp plus a 2 channel amp for the subs, so thats two separate amps. I was drawing out a plan see below. I'll be using the stock unit, I dont care to much for flashy lights or shinny face plates. Is the MB Quart NAU 660 6-Channel Marine Audio Amplifier 540 Watts or the Infinity REF 5761A-B 560 Watt 6-Channel Power Amplifier a good amp? I would like to power both front and rear speakers,(that 4 speakers total) PLUS the additional front door Mid speakers. They're factory Mid drivers. Ive heard them before on cars that were equipped with them factory and they sound good, My car didn't come factory equipped with them so thats where the 6 channel amp comes in. I would like to control power/bass to those door Mid drivers separately since the factory stereo doesnt give me that option. Do the amps mentioned above give me that option? Can I control those channels independently such as adjusting the crossover. Im not an audio guru so help me out! thanks. Oh yeah and the 2 channel amp is for the pair of subs in the trunk which will run of the rear speakers for signal, Im using a hi-lo converter for that. Thanks ONE AMP IS A 2 CHANNEL THE OTHER IS A 6 CHANNEL. (YES IM AWARE THE PICTURE SAYS 2 CH AMPLIFIERS BUT THAT'S A TYPOGRAPHICAL ERROR . -ONE 2CH -ONE 6CH.

Also what does it mean when an amp says A or B, such as Infinity REF 5761A-B. A-B?