montero is made by mitsubishi. anyways if its allready got an amp theres no trouble hooking up another. if it doesnt have an output all you simply have to do is run the wires to your aftermarked amp first which will almost certinly have outputs then from the new amp to the old amp. now you will need to pull up a bit of interior for this part. but you will need to replace the power wire the amp is using with probably double the guage dpending on what size it has. id go with 4 guage if your not planing any realy high power subs. you will also need a distrobution block which should split out to two 8 guage wires run a power to each amp and give them there own grounds. you can also go to another distrobution block and do one ground or run it streight back to the battery.