General question about my head unit with speakers

Hey guys, I'd just liked to say in advance, that I appreciate all and any info you can give. When I bought my car (a 1989 Nissan 300zx Turbo) there was no radio, and no speakers (the car has two in the doors, and two right above the rear shock tower). Now, I bought this http://www.pioneerelectronics.com/pio/pe/vgn/images/portal/cit_3442/36620Deh2100.jpghead unit for $20 from my friend (it's a pioneer deh-2100 and it says 45wX4 on the faceplate, which I'm assuming means 45 per each channel). Now I'm going to be getting a great deal on a 4 speakers, two of them rated at 115w RMS and the other two rated at 110w RMS. My question is this, my dad said that w/o and aftermarket amplifier, I'm going to have to turn my stereo all the way up, even to hear a lil' bit of sound out of these speakers... is he right, or full of it??? Thanks again guys

full of it. it isnt uncommon for home audio to have tube amps with a whopping 2w RMS output.

2w of sonic energy is a lot, even at 50% efficency that is 1w of sonic energy. The sonic energy emited by all of the people at your average NFL football game is barely enough to boil a cup of watter from room temperature. That is roughly a consant output of 16w of sonic energy. that is enough to keep a stadium at around 90dB, which is reletively loud.

That was just putting it into perspective. Through your amp isnt doing 45wx4 w/o its own internal amp, it may be doing 20wx4 or so into a 4ohm load. even still giving thoes speakes their rated RMS compared to HU power will only gain you 6-8dB

your stock speakers get plenty loud with a massive 15w RNS per chanel or less.

^that's just the thing though, my car didn't come with speakers in it, and I got a good deal on these. Thanks for the clear-up though.