He is asking about front and rear speaks, not subs (at least by rear I don't think he means subs).If you only have the space for a single driver, and are all fired up about 2ohm woofers, then look for a dual voice coil driver - get the idea?
If we are talking about the interconnects between things then yes but not necessarily when dealing with amplifiers.Isn't less resistance better?
Understand something about speakers in that if the amp is rated at some given wattage you aren't delivering that all the time. I think this is largely misunderstood by most people that don't know car audio.each speaker will have its own channel so none will be run in parralell. I am just trying to get the most out of my amp. It boasts 100w rms per channel @ 2 ohms and 65w rms per channel @ 4 ohms so it leads me to believe that I should get 2 ohm speakers right?
Each doubling of power results in a a 3db increase in volume with an approximately 10db increase representing double the loudness. So if your speakers produced 90db of sound with 1 watt (commonly referred to as the sensitivy rating) then at 2 watts they produce 93db of sound. This doesn't account for any gain your car will produce because of the enclosed space.
As we continue this thought experiement keep these values in mind:
A walkman at full volume will produce approx 100db into your ears.
The front rows of a rock concert approx. 110db
The pain threshold begins at 130db
Continuing at 4W your speaks produce 96db, 8W=99db, 16W = 102db (you are now blasting a walkman in your ears) 32W = 105db and at 64W = 108db you are close to simulating the front row of a rock concert right there in your car. Now, if you wanted 2 ohm speaks and could double to 128W then you would be at 111db (not much more than 108db huh?). Since you are only getting up to 110W then you are coming in near 110db, which isn't much better than 108. This is all assuming you are driving your setup and full volume all the time, which you will be foolish to do so.
So my point is you don't gain much volume wise (and even then it is only a small fraction of your listening time), but what is the tradeoff? A huge loss in sound quality. Through the entire power range a 2 ohm speaker sounds much worse than a 4ohm speaker if you don't have a great amplifier. Distortion goes up a ton the lower in impedance you go. Again, you don't hear it as much in a sub because of the frequency range but with your high end components this shows up big time as harshness and grittyness.
You might ask why car audio setups tend towards 4 and 2 ohm components when home speakers tend toward 6s all the way up to 16 and more? To get lots of power into an 8 ohm speaker requires a larger voltage which starts to cost more money because of the switching supply in the amp has to produce these voltages which means more costly transformers, capacitors, etc etc.