I have hooked people up with some of the nicest SS bikes you have ever seen for far less than $400.00.
The best route is to convert a decent quality road bike without f'ing up the frame... there are 1000's of great bikes and frames out there that are far better than any entry level SS you can get at BD.
This is of course unless you want some cool tarck bike for doing mad bar spins... but if you want to ride and really enjoy the ride a conversion makes excellent sense.