Nothing wrong with Trek or Giant. Specialized is good to.

Here's Specialized's version - a Vienna 1 -
http://www.eriksbikeshop.com/ride/pr...ffset=2&s_id=0

When people ask me for recommendations for a casual but reliable bike, I tell them that $400 retail is the point where they can still buy something fairly decent and reliable, but don't go below that. If you want to save money, sometimes you can find last years models that were $400, but are now discounted.

Like locally to me in MN, last year's Vienna is on sale for $350 -
http://www.eriksbikeshop.com/ride/pr...ffset=2&s_id=0

Sometimes you can find something used, to, like on craigslist. But especially at your price point, it's a cost vs time thing - is spending 8 hours of browsing and looking for the bike plus the risk of getting something broken, worth saving $100-$200?

For advice, I would add the following -
1. The most important thing in buying a bike is getting one that's the right size. Don't make the mistake of buying something "that's a good deal" if you feel it might be to big or to small for you if you can help it. It will be less comfortable to ride, and if the size is to far off can be painful to ride. As well as making you slower. The bike should be comfortable to ride with the seat about level with the handlebars, and your feet should have a slight (but not a lot) of trouble touching the ground while sitting on the seat with the bike in a regular upright position.
2. One thing that makes riding unenjoyable is getting flats, and the low end tires that come with entry level bikes are often fairly flat prone. I often suggest replacing the stock tires with better flat resistant ones...it's hard for me to say whether this is necessary for you because I don't know which tire your bike would come with, but one suggestion is the Schwalbe Marathon tires, they're like $35/piece (retail).