this is how this works...power extracted from the amp is based on the wiring of you sub(s). most times, multi-channel amps will usually have 3 power levels - one at 4 ohms stereo, another at 2 ohms stereo, and finally one at bridged 4 ohm mode; and when i say stereo, i mean the channels are not bridged. single channel or mono amps do not have the bridged rating. if you don't see it already, the power rating usually work like this...power at 4 ohm stereo is doubled when the amp is running 2 ohm stereo (same number of channels in use) and is quadrupled when you bridge two channels down to only one (still at 4 ohms). the rms rating on a sub is power that it can handle well under normal, prolonged playing while the peak power rating is for those times when the music dangerously bursts out for a very, very short time.

so let's dissect your system...you are running an real mtx enclosure with three 10" subs right? based on their website, the subs are wired together to ultimately produce a 4 ohm load. your amp is a two channel amp that can put out power at either system voltage of 12.5 or 14.4. i highly doubt your car is running 14.4 consistently (requires a lot of upgrading and/or multiple batteries and/or alternator work), so your amp is more than likely putting power based on the 12.5 rating. specifically, 37.5x2 at 4-ohm stereo or 75x2 at 2-ohm stereo or 150x1 at 4-ohm bridged. and why would an amp overheat if it is capable and rated to put out 325w...have you rewired the subs int he box yourself??? so basically, all three subs are either getting only 37.5w or 150w (the box is a 4 ohm). to determine power to each sub, you basically divide by the number of subs...37.5/3 or 150/3. you should see that is not much! i take that each sub in the box is a t4104a that is rated to take 200w rms and 400w peak. now if you work that equation backwards...knowing that each sub can take 200w rms, you basically multiply that by 3 to figure out the amp's power. so you need an amp that will put out 600w with a single channel or two channels bridged. if you like, you can get an amp that puts out a little more than that because most subs are built tough. that amp that is 2x750w amp is more than good enough. you actually don't want to bridge that amp because this would mean each sub is getting 500w rms...the subs could blow if you turned it up high and long enough!