I bought a Takara a year and a half ago. My first single speed and my first road bike. I have put bullhorn bars on it, Cane Creek TT levers, Tektro 510 brakes, 700x25 road tires and tubes and XLC pedals on it. Just been using it for fun but recently started commuting 4 miles each way, mostly flat. My main issue is is the weight and feeling slow especially from a stop in traffic.

Would it make sense to buy a new frame and fork and possibly bigger tires for commuting like 700x32 or just buy a better bike from bikesdirect or someplace? I am on a budget (hence the reason I'm commuting by bike). I can't spend more then $500 all in but I'd like to spend as little as possible. I've also considered getting a cheap geared bike from bikesdirect since I'm riding some hills and carrying more weight while commuting. Though I figure I would have to bring it to a LBS to have it set up especially a geared bike since there seems like a lot of assembly required with the bikes direct bikes.