if you want your amp to output it's 2-ohm rated output levels, then it has to see a 2-ohm load from the speakers. if your speakers and sub are 4-ohms each, then your amp will see a 4-ohm load per channel, and will output it's rated 4-ohm output level.
to bring the speaker impedance up or down, you need to hook up more than one speaker per channel (or replace the speakers with 2-ohm models). if you wire two speakers in parallel the impedance will be cut in half, if you wire two speakers in series the impedance will double.
assuming your two door speakers and subwoofer are all 4-ohms each, there is no way to get a 2-ohm load without adding more speakers or replacing them with 2-ohm speakers. (don't even try to hook your door speakers and subwoofer to the same channel[s]).
what are your door speakers impedance? what is your subwoofer impedance? how many channels is your amp?