I have recently decided on changing my speakers to have clearer sound. Ive got a JVC H/U and wanted to put MTX for the back and component Alpine S series for the front(both 80W RMS). I plugged in the speakers to check if the sound is better but looks like i have to set the volume to higher level so i get the same sound level compared to the previous speakers specially in the low freq. range. I was wondering if that would change the sound quality if i use the speaker adapter and drill it to the door? ( the reason I didnt attached them to the door was that I was not sure If I want to change the speakers if i don't get a decent improvement)

Are you running new speakers on the OEM head unit?

If so, the speakers will probably be quieter. Because the OEM speakers are 2 ohm, and your aftermarket speakers are probably 4 ohm or higher.

No, i already changed the Head Unit, but as you said, the spec for the HU is 50x4 @ 4ohms speaker. My stock speakers sounds way better than the aftermarket one. I think i should wait until I add an amp...