there are many different types of speakers and many types of amplifiers, i really cant explain it all in one post, but there is a good "tutorial" i suppose you can call it, all about what to buy and how to buy it. there is also many amps that will fit your needs. http://www.atomicaudio.net icant3dmodel

it all depends how many watts the amp can give for each channel and how many speakers you have, also if it can withstand the wattage tha amp is giving. you dont want them to blow.do you?

This is a fairly common question that, unfortunately, is not easy to answer because of the quality (or lack of) information supplied by manufacturers. Since I have already answered similar questions, I will poach my answer to those, with a few changes… Any audio system - automotive, home, or professional - requires adequate power to reproduce audio with minimal distortion over the full audio range at a reasonable listening level. Unfortunately, the specifications published by manufacturers can be misleading and are often ambitious. This is particularly true for car audio, where amplifiers and speakers ratings are often wildly overstated or, perhaps more accurately, stated in a very unrealistic fashion. You should be very cautious when you see an auto amplifier rated at 1,000 watts (W), since this rating may represent peak power at 10% THD (total harmonic distortion), measured into a 2-ohm resistor on a test bench, over a duration of a few milliseconds (i.e., until the power supply capacitors are drained). Such an amp might only deliver 50 to 100W RMS continuously into a real speaker load at <1% THD. Be aware that the power system in an automobile is not capable of delivering 1,000W for any appreciable period of time. It is absolutely essential that you obtain reliable specifications for your equipment. An amplifier rating of “X” watts is meaningless, unless the frequency range, speaker load, and distortion levels are included. These are typically: - 20 to 20,000 Hz frequency response. - 8 ohms resistive load. - <1% THD. Intermodulation and, particularly, transient distortions are often more audible than THD and should, therefore, be lower. Note that THD is a crude measurement, so a 1% THD level on one amplifier may sound quite different than 1% THD on another. Unfortunately, many manufacturers do not report anything other than THD. You also need to know the speaker impedance and sensitivity. Note that the impedance of a speaker varies with the frequency of the audio signal, so that the impedance of a speaker rated at 8 ohms (nominal) may range from as little as 4 ohms to over 50 ohms. The sensitivity of the speaker is also critical and is dependant on the enclosure, if one is used. A low-sensitivity speaker requires more power to drive to the same loudness as a medium- or high-sensitivity speaker. A general rule of thumb for calculating the peak listening level in a room is: > Peak_level = Speaker_sensitivity + Amplifier_power - Distance_factor (dBW) (This is not completely correct for an auto interior, but is close enough for our purposes.) Speaker sensitivity is specified in terms of dB, measured 1 metre from the speaker. The distance factor is 0 if you are sitting one metre from the speaker, which would be the case in an automotive environment. In a room, you would subtract about 5 dB for each metre you move further away from the source. So, if you were 3 metres (about 10 feet) from the speaker, the distance factor would be -10 dB. Amplifier power, in watts, is converted to dBW using: > 10 x log(Power_in_watts) If you desire a peak level of 110 dB, which is quite loud, and are using a fairly sensitive speaker (e.g., 90 dB), then: > 100 = 90 + Amplifier_power > Amplifier_power = 20 dBW. Values expressed in dBW can be converted to watts using: > Watts = 10^(Power_in_dBW / 10) In this case: 10^(20/10) = 10^2 = 100W Note that a small change in speaker sensitivity has a significant impact, since a 3 dB increase requires double and a 10 dB increase requires ten times the power. A change of 2 to 3 dB is audible, but smaller changes are not. Since most systems tick over well under 1 W during normal operation, a 100 W amp may seem powerful enough. However, music is full of transients. A 0.1W signal would need to jump momentarily to 100W to handle a 30dB peak, which is not an uncommon demand. These factors also explain why there is no effective difference between an amplifier rated at 100W and one at 90W.

Ok say you have 2 subs that are 1000 watts each. You would want a 2000 watt amp. If you have four you'd want a 4000 watt amp. If you have 2 1000watt subs but only a 1000 watt amp tha amp is gonna be tryin hard to power those speakers and you will overheat it and the fuses will blow comstantly. But if you have a 2000 watt amp with only 1 1000watt sub then make sure you keep your amp turned down so you dont blow the speaker.

You can actually use specific test measurement equipment for your amplifier so that you will know how many watts it caters. http://www.techrentals.com.au/

Depending on how loud you want it and how hard you want it to pound, I'll go like this. Always go by RMS for the amp when picking it out. Always go by peakpower for subs and speakers. For subs your best bet is to get a class D mono block, or and a/b amp if your wallets thin. For speakers a/b amp. Perferly buy an amp that is for it. You'll get more resale value if you have a complete set with it.

I would actually go for a slightly under-rated amp since driving speakers to their limits sounds horrible and over-driving them with too much amplifier will blow them. But the answer depends a bit on how the components are actually rated. See, some manufacturers will artificially inflate their rating to what a speaker can take or an amp can deliver without blowing while others go for a more conservative number that allows a little headroom for transient spikes or that sounds good without humming, buzzing, etcetera. In short, it's less about knowing math than knowing marketing.