Well something came to mind after looking at the SI's box recomendations. I am a SQ guy so the 1.5 cu ft box sealed sounds best to me. At 1.5 cu ft, that is almost 1/3rd of the size of the box that is currently in my car! I have a 4.4 cu ft box for a single MTX sub now. Anyway, The system I am replacing is the first single sub stereo I ever made. Needless to say, I only bought 1 SI Mag12" to replace it. However I am wondering now, should I consider a second sub? I will be running a US Amps USA-300x Rated at 900 watts at 4 Ohms at 12 Volts. Can this amp power 2 of these is some way? This dual 2 ohm voice coil stuff is kinda new to me. I am used to old school SVC 4 ohm subs lol.

The front stage will be CDT Es520's with 150 watts and CDT EF8's with 300 Watts

If you're going for "SQ" you shouldn't need the extra SPL from a 2nd sub.

For the only safe wiring configuration, you'll have to run the amp at 8 ohms. Try it out, if you need more, get another one. You'll be surprised at just the one though.

you think too much Tim. I think you're imagination is running wild on you. I think you will be more than suprised with just one 12. Remember that same 12 you have in a 1.7cu ft box outdid my 160v.2 in a 2.2 ported box tuned to 29hz in audible output. Even on the mic the 12 was incredibly loud getting very close to 140s in a 1.5cu ft sealed. i actually did 141.4 on it at the windshield. Your car is smaller than my Galant. You'll be amazed, wire that thing up instead of asking..lol. Hear and see the difference. Your MTX has nothing on it.

who wants more is the title ... i want 2 or 4 more depending on what class i run next year

I was happy with my 2 12's with a mere 300 watts each, it was the loudest system I had to date. I think (as everyone else does) you'll be quite surprised at the output of just one with 900 watts.

I was happy with my 2 12's with a mere 300 watts each, it was the loudest system I had to date.  I think (as everyone else does) you'll be quite surprised at the output of just one with 900 watts.

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Oh this sub would run with say 500 Watts? I am still waiting for my US Amp to arive but I have a Soundstream Reference 500 I could put on this sub to test it out.

It will surprise you on 500... dooooo it...

The sub will just plain surprise you

Funny I have been waiting a week with this sub for the US Amp to arive. I guess I should take my MTX sub out and cut up that box to make it a 1.5 box instead of 4.4 and wire it up! lol Bummer is all I have is a Puch 100 DSM on my fronts which is not very loud. At least not what I am used to. I have a USA-600x on the way as well to run my CDT's!