Since you are using the bike as transport which needs to be reliable, why not get something of good quality? Why spend (ie waste) money on another cheapie? Remember the amounts you are NOT spending on fuel etc etc, not to mention the health benefits. So it does not make any sense to me that you want to buy another entry-level bike. They are simply not up to the sort of work you are meting out. Seems to me a Bike Friday or something along those lines is a sensible option for you. Save up if you can't afford it out-right.