it's not extremely underpowering the sub, but why not get an amp with more power. At least 800 watts if not a little more. I know if I would have gotten an amp that maybe was even slightly underpowered I would regret it and would have wished I got a more powerful amp
You should be fine. I know that with most of the audiobahn subs and just about any other sub for that matter will do fine underpowered as long as the gains are set correctly and you aren't trying to push the crap out of the amp. I used to send about 220w to each of my 1005q's and they did just fine eventhought they are rated at 900w rms.