I would stay away from anything in that hyperlink that you posted. It looks to be Wallyworld level rubbish.

Check out Ironhorse, it is in a totally different league from what' in that link. They tend to give you higher end bits for the money versus the competition.

Also, look into: Trek, Fuji, Marin, Gary Fisher, GT, Giant, Mongoose (not the X-mart kind, the LBS kind)......

Don't forget eBay as well since you can snag a nice used bike for 300 bucks there.