stop thinking that an amplifier has to put out its maximum power all the time.
there are knobs and buttons on the amplifiers that can turn down its output function. if you have a speaker that has a thermal capacity of 1200w, and an amplifier that has a max RMS of 1200w, you will be better off using an amplifier that has a max RMS of 1800w with the gain turned down.
think of it this way. for example, your car has a speedo that goes up to - lets say 150mph. you will prolly never go that fast, this is related to MAX power. lets say you got on it and went 120mph, and thats as fast as you would ever feel comfortable driving, that is your RMS power. now, if you drove around pedal to the floor all day every day because you feel comfortable at 120mph as a top speed, do you think the car would last long?
prolly not. so you will be better off with the amp that has more output power at a given impedance than one that is exactly matched to a speakers thermal rating. not to mention higher impedance (the 4 ohm amp) will have less current draw for your electrical system - or it should be less. if its bridged 2 channel class AB, maybe not. in my opinion - i would keep the OZs and find a better way to utilize them, because you will get more output out of a pair of the OZ's than a single one of all the speakers listed in a small sealed box (you are trying to save space, and the only way you will be louder with a single sub setup from the speakers listed is to have a larger ported box, which will take up as much room as the two subs in a sealed box.
so, you need to find an alternate speaker to use that will give you higher output in a smaller space.
the stereo integirty BM comes to mind. or their new mag when that is released. maybe that stupid jl audio tw-whatever shallow sub even though its way overpriced.
look around. your options are not limited to the idmax, w7, and tc-9 based drivers. these are all large and will not be louder than two OZ me's - in my book (i have had two 12" me DVC4's) they ME is louder than the IDQ and a bit less than the IDMAX, so a pair of them will defiantly be louder.