Been reading up on brakes and after today on the trail after down hilling on some pretty steep stuff I was pretty disappointed in my stock brakes (Hayes MX2, not sure about rotors but probably 160's). So I am looking at getting a BB7 for the front in 203mm. My main question is about levers. Is it necessary to replace those too with the new brakes or just recommended? I was looking at two different levers, the Avid Speed Dial Ultimate Brake Levers and the Avid Speed Dial SL Brake Levers. Is it worth twice the price to get the Ultimates and will the new levers also improve the stock rear braking?