Can I Have 1000 watt amp for a 300 watt subwoofer?

If the rms rating of the amp is 1000 watts which i ume it is (infinity is high quality company and usually lists rms) than yes you can. Just be sure to keep the gain on the amp down to about a half. You would do better to look for a 500 watt rms subwoofer though. It probably wont cost you that much more and you'll get the most out of your infinity amp and you wont have to worry about blowing your sub as much.