for the $50 range I'd recommend the Hitec 5625.
http://www3.towerhobbies.com/cgi-bin...&I=LXUZ76&P=ML Not a huge Hitec Fan personally but probably the value for that range. about $45, Digital, metal gears, over 100oz. of torque, Significantly faster than a "standard" servo with plastic gears. shouldn't be a huge drain on your BEC. also comes with an aluminum servo horn as well. For RC cars, you have to pick if you want metal or plastic gears. some are only going so say metal, but remember that a RC car is going to hit stuff, and something is going to break eventually. having a weak link such as plastic servo gears that are quick and CHEAP to replace might be a good thing. personally I'd prefer metal. next price range up (70-80 bucks) would consider the Spektrum 6040
http://www.spektrumrc.com/Products/D...odID=SPMSS6040 stronger, faster, titanium gears.
HTH,