Question about kicker solo x 18 and the kicker amplifier?

[Amrit S]

First i was looking at kicker solo x 18 (10000 watts and 5000 RMS) and two kicker zx2500.1 (2500 RMS). after saving up the money i went to a car audio guy to ask him for installation but he told me that i need only one amp. i don't get it one amp only has 2500 RMS then how subwoofer will work to its full potential. i also thinking about alpine speakers in the doors but he told me about some audiopipe speakers. if u know about speakers please explain it to me why i need one amp and about audiopipe