I have been looking at two different setuprs for a long time and really dont have one rated above the other. ---2 12" Diamond Audio M6 Subs that put out 500 watts RMS each or ---1 15" Diamdon Audio TDX Sub that puts out 1200 watts the price is only 60 dollars more to go with the 2 12", but i dont see that I would gain anything over the other. Does anyone have any imput?

I would venture to say that the 2 12" would be louder. However, they cost more, and would likely require a larger box too. It really depends, and would help if you could provide a link. Also, the speakers do not put out watts in the way you are thinking. They can handle a certain amount of power, and that is what the power rating is. Speakers are very inefficient, usually below 1%. So for every 100 watts of power you put in, AT LEAST 99 of those watts are doing nothing but heat the speaker up. The actual acoustic power a subwoofer puts out is a couple of watts, nowhere near several hundred.

15" TDX 15D2 General Kevlar Nomex sandwich cone Die Cast aluminum basket Neodynium magnet huge dual voice coils Dual spiders with woven tinsel leads Specifications Power(W RMS): 1200 Impedance (ohms): Dual 2 Sensitivity (dB SPL): 91 (2.83-V input @ 1 meter) Freq. Resp: 18Hz-200Hz(±3dB Dimensions Diameter: 15" Depth: 9.5" 2 12" M6 12D4 General Titanium Magnesium cone 3" voice coil Dual Nomex spiders Lead wires woven in Spider Specifications Power Range (watts RMS): 800 Impedance (ohms): Dual 4 Sensitivity (dB SPL): 90 (w/2.83-V input @ 1 meter) Freq. Resp: 25Hz-250Hz(±3dB) Dimensions Diameter: 12" Depth: 5.9" For more info you can go to www.diamondaudio.com

Well according to the user's manual, it looks like the 15" will have more displacement than 2 of the 12". Since its cheaper and will get louder, I don't see any reason to get the 2 12".