Kat... sounds like it's too late to give you some advice, but to be honest with you, I'd go with 2 10" subs over 3. You honestly don't have the volume for the 3 subs behind your seat. With the seat back, your subs will be acting like a bandpass push-pull sequence but will be underpowered, which will make then distort in a bad way (cause you have to remember that your subs are fighting against the seat).
I used to install Competition Stereo systems back in CA, I have dealt with this many times. First off what you need to do is figure out how much volume your speakers need, versus what you have and go from there, have a custom enclosure made. You will have to port your boxes to make up for some extra airflow. If you do not you subs will have too much resistance inside the box. If not, then after time your subs will sound very muddy. This is do to the lack of travel that they have in such a compressed area. Do also take in account that with your situation you need to have your subs crossed over no higher then 300hz... .
Trust me on this one... I can give you some references that will back up what I am saying!!!
One other thing that will back up what I am saying is this. Take in account that Fosgate only makes one enclosure that consists of 3 10" subs and it will not fit in your truck!!! You'll see because of the air volume that these subs need that Fosgate only makes a hatchback style box.
Which tells me that this enclosure that you are looking at was just thrown together by the local stereo install dude that is making $10/hr. Go to someone that cares about sound and knows what they are doing... not to some local shop in which the people don't know jack!
IMHO I also have to say that I would stay away from Fosgate subs. Fosgate makes very good mids and tweets, but their subs are very low in quality and
CAN NOT in any way compete with brands like Soundstream, Kicker, Orion, JL Audio, Boston Acoustics... etc. I know that you are not after Competition sound... but if quality is what you want... you gotta pay for it.
Guys I know that I keep babbling on about this... but last off is this. According to the box that is on Fosgates website, it's nominal Impedance is 2. 67ohms. Which I have to say that the Punch 360 will not handle a 2 ohm bridged load. It will overheat itself. So Eric, you better find out how these speakers are wired and what the final impedance is so that these clowns don't sell you something that will burn itself up due to their lack of knowledge.
Kev
Here's a link to a pdf that is the box dimensions that Fosgate makes
Rockford Fosgate 10" tri-sub enclosure
Also note... that you may have do so something different with your infinity speakers cause they are preamplified.
[This message has been edited by K_Arts (edited 03-12-2001). ]
[This message has been edited by K_Arts (edited 03-12-2001). ]