Amp Help?

I just bought a alpine type r 12" sub, 4 ohms, and a M-450 alpine amp. (220w @ 4ohms) The guy at best buy told me the amp would give the sub very little power and it would sound bad. He said to buy a M-650. Will the M-450 work or do I need to get a better one?:screwy:

it would sound better with the m650 and even better with the pdx 600