Hey mate, you have a few options. ere is a few options. Bear in mind, when it comes to actual product to use, I won't actually recommend anything. Just make a suggestions with some options.
Just clarifying, some of the people above mentioned replacing the speakers with splits in the front and co axials in the rear, 4 champ plus a sub and amp. I will agree with them that this is the ideal situation. But it is not budget conscious which is why I did not suggest it.
While not familiar with this amp, it specs look like they are upto the task
Fusion CA-AM40700 Car Amplifier - RYDA Car Audio($139.85)
This isn't a bad unit, it's quoting 90wx4 but thats at 2ohm so at 4ohm (your speakers) I would expect 40-55ish
Kicker ZX3504 Car Amplifier - RYDA Car Audio($298.85)
Now, this is unit is a 5 channel.... Going this path has it's pros and cons. If I had to suggest one product, I would say this unit The price is right as it contains your amp for the door speakers and the amp for the sub. It's rated at 4x60 watts and 250-350watts for the sub (dependant on sub impedance) Yes, the 60 watts is a lot more then the factory speakers can handle so it will require VERY sensible use of the gain controls on the amp and volume control on the amp. Any speaker abuse will quickly lead to their demise. BUT with that being said, IF you keep the signal clean you will find the bloke beside you screaming abuse before you do damage. 250-350 for a sub is often ample.
Don't be sucked into buying a massive power cabling kit. In the instance of this amp in the VE Commodore I could do the entire job with about two meters of 8ga ($7 worth of cabling) but on the same hand, you could use 4ga for a little bit more and save any arguments that would ensue from me suggesting that (puts on flame suit) You would not be needing ANY pairs of RCAs, nor will you need LOCs. You will need speaker cable.... and a lot of it. You need speaker wire from headunit to the amp and then back again. For the fronts mostly. The rears can be taken directly from the back of the speakers on the parcel shelf. The amp has a small footprint so can be quite comfortably be mounted and hidden from view in a VE.
Alpine MRX-V70 5 Channel Amplifer - ($368.85)RYDA Car Audio
Sub choice... well, the world is your oyster and your ears are the pearl within.... hehe, thats about as deep as I get.
Ok, so to be perfectly honest, I wouldn't bother looking at power ratings on a sub at this point. Anything with a name brand is going to cope with that power and the fact that you be cranking it to it's eyeballs means that underpowering shouldn't really be an issue either. But if you do want to pay attention to these things then these are the specifications you need to look at.. regardless of which amp you choose.
Watts, always look for the RMS rating. This rating is the real power rating you could say. It's what the amp can put out all day long without damage or the sub can handle all day long without damage. There are many other factors that people will bullshit and talk out of their arse about (e.g. RMS@hz, spl/M)...ignore it basic general everyday setups, it don't mean ****. There I said it. (pulls on second layer of flame suit)
Ohms, 2ohms does not sound better than 4ohms or vice verse. There is absolutely no diffference. The only thing that cares about this number is the actual sub and amp itself. The lower the Ohms (impedance) the more power the amp will ATTEMPT to deliver. For instance, if a 4ohm sub is put on that Alpine, it will deliver 250WattsRMS... if you put a 2ohm sub on it, it will deliver 350WattsRMS. It won't put 350WattsRMS into a 4ohm sub.
Does that make sense? Yes? Good. No? Don't worry... Been doing this 15yrs and I still get confused.
What size sub? 10", 12" or 15" (there are other size but these are the generally accepted 3) As a rule of thumb but not a definite. The smaller the sub the "tighter" the sound it can deliver... BUT... you also reduce it's ability to go lower than a larger sub. A good way to look at it... is what do you listen to? People who listen to a lot o techno and electronic music seem to find a 10 more their style. Hip Hop and rap crap (sorry if your a fan) will lean more towards a 15 for it's ability to go low and stay there. People who just can't decide what they want or listen to everything find themselves using 12s. 12s are most popular without a doubt.
So that leaves... enclosure type! Sealed or vented? What sounds better? Sealed. (in most instances) A sealed enclosure as another RULE OF THUMB typically has a higher sound quality than a vented enclosure. But it has it's down falls. Because there is more resistance on the rear of the sub in the box, it typically requires more power to achieve the same volume as a vented sub. Furthermore, because of this extra resistance, it typically cannot play as low as a vented enclosure. (this is often times never picked up by the listener though unless you are after those ultra low frequencies like Nic92 for example lol) So why does it sound better? Well... many reasons but the usual response is it's more "controlled" <~~~ Not a technical term lol
Vented enclosure have many benefits also! First off, to achieve higher volumes, less power is required. Secondly, it can play lower frequencies (again though, this is only relevant if listening to music that goes that low.) The downfalls are that sound is not quite as controlled as the sealed box the second is that it often requires a larger box. Usually between 30-50% larger then the same sub in a sealed box.
and look at that... another novel written. Ooops. Didn't mean to bore you and I'm sure I've just provided the Tasmaniak haters with plenty of fuel for their fire to argue with me. But hey... I still sleep at night.
