Looking to upgrade my system possibly.
Right now I have 2 12" being pushed by a 750W , stock tweeters, pioneer 3-way door speakers/rear deck speakers.
I'm trying to upgrade and find a good 5-channel system amp and to trade out my 12" subs for a good 15" sub, along with running the extra 4 channels to my door speakers.
With this in mind, I've found a good amp and sub pair, however selecting a box has been giving me problems.

First problem I need help with:
Most of the time that I look at audio equipment, I use onlinecarstereo.com because my friend bought his amp from there, it was cheap and worked fine.
The sub I found says this:
Rec. Sealed Enclosure is 1.6 cu. ft. (44.74 liters)
Rec. Sealed Enclosure Range: 1.50 cu. ft. - 3.00 cu. ft.

And I've found a box that is a sealed 1.7cu ft box.. Would this work? I have an acquaintance that is sponsored and goes to competitions and will build me a box if I can't find one, though.

Second problem:
My car is small, I drive a honda civic. With what I have hooked up now, driving at night my headlights dim when the bass hits.
The solution to this in my mind is to upgrade my alternator and/or my battery.
Looking on autozone.com , I found an alternator that works for my car which will crank out 70amp.
I can't find the specs for my car that show my stock alternator output, but from what I've read online, this doesn't seem like much of an upgrade.
Does anyone know where I can get a good one/find out how big of an alternator I need to have in order to push a 2,500W amp.

Sorry for being so long-winded. I've always loved audio and I love my system I have now, and want to make sure that anything I do to it will be done right.
Any help i greatly appreciated!

firstly don't bother with 5 channel amps.

what model sub/amp are you looking to buy right now?

if your friend knows what hes doing then let him build you a ported box for whatever sub you pick out.

ya you'll need to upgrade the alternator. to find about how much amperage you'll need use this: rms watts/14.4=amps. make sure you are only using rms watts not peak watts because peak watts is useless garbage.

there are lots of brands for high output alternators. and you can expect this to end up costing $300+ to upgrade.

Do not buy from auto zone unless you plan on replacing it every three months

@ Subwoofer , why not a 5 channel?
I was looking to get it since it's pretty much a whole system type of thing and right now I have a 2 channel.
Granted I could purchase a 4 channel and a mono to power the sub.
Thank you for the equation for my alternator, basically RMS = 1/2 peak since it's at 45 degrees on the sine wave, correct?
( It lists the RMS on there, just asking.) And where does the 14.4 come from? I've hooked up subs and done some work with solar panels, but when it comes to automobiles I don't know anything.
Hence why I'm trying to learn.

I'll check on the sub/amp pair I want to buy, I bookmarked it on my laptop which is dead at the moment.

@tbiddystrong
I know a 70w alternator isn't enough so Autozone is out of the question.

i would just like to add on to this.

the box you found will work just fine it will just be tuned SLIGHTLY different than it could ( a tenth of a square foot is rather trivial )

ie.. the box you found will be tuned slightly higher in frequency as it relates to sq of your sub than it could be. which actually might be preferred, depending on the genre of music you listen to. as far as SPL goes there will be very little difference as well.

Peak is just some bullshit number that companies throw on to make their subs look better.
14.4v is the average on what cars run (I believe)

Yeah, don't get a 5 channel. Mono would be better for the sub, then get a seperate amp for the components/inside speakers.

Whenever you get it powered back up, post what sub/amp you were looking to buy.

If you are trying to push 2,500 watts, wouldn't go with anything smaller than 150A alt...
But again, let us know your sub/amp setup first.

@ Sharoflard, I didn't think that .1cuft would make a huge difference, considering they said 1.5-3cu ft.
My friend will probably be able to do it for cheaper since he's actually making it himself and gets it for dirt cheap.

@ Cory , alright that makes sense. I forgot each cell produces more than 2v on average on a 12V battery.
And I will post it, can't quote/edit on my PC which is why I'm quoting like this.
The one's I found are little-name brands but the reviews are good and they're cheap.
I wouldn't be turned off from paying more if it makes a huge difference or what I'm buying is crap, though.
I don't like systems that are just loud, I like ones that sound good, which is what I have now.

Absolutely

Quality > quantity EVERYDAY
User - Subwoofer is great with anything car audio.
I've seen him post a huge variety of sub/amp combos for any price range.
I'm still intermediate at systems, I've only had a few/hooked up a couple dozen... So i know the basics, but subwoofer is pro