I wondered if amplifiers with headroom to run at lower ohms could add subs to 'match' the resistance of 1 or more other subs already there to take advantage of more power at lower ohms.

Let's take my N4 for instance. I run a dual 1ohm sub on it to get the amp to run at the 1000w level (using stated numbers from manufacturers just to simplify) so I run this sub at an effective 2 ohm load. If I were to add two more subs, say 2 dual 2 or 2 dual 4 ohm subs, and wire them so the newly added pair were an effective 2 ohm load then paralleled the pair in with the single sub already running at 2 ohm would it drop the effective load of what the amp would see to 1ohm or would the differences in speakers change what the amp sees in the end?