For my girlfriend for a Christmas gift. Her bike is a total POS that doesn't shift or brake well since it's a Walmart special. I'm not looking to spend much more than 3 or 4 hundred bucks, though. Should I try and build the bike myself using low end bargain parts I find, or should I buy something from a LBS? Is it even possible to build something for under 400 bucks? The biggest thing is that it must be inconspicuous. I'd love to build her a nice Cannondale or something with disc brakes but I'm sure it'd get stolen pronto on campus. So what are my options here?