if I were you, id buy a short(ish) 3/8" breaker bar, and then a good size 1/2" breaker bar. Ive had fine luck with the auto parts store untis as far a breaker bars go, there isnt much to them that can differ quality-wise, IMO.
Make sure you have the right 1/2" drive sockets for lug nuts, etc., if you go that route. A long (2ft or so) 1/2 drive breaker bar with a 1/2 to 3/8 converter will often shear the adapter's 3/8" nipple off before breaking free the bolt it was all attached to... since yore generating so much torque with that baby. It does become VERY useful when doing items like diff plugs, brake caipers, suspension parts, or even lugnuts, all of which can get siezed in there from the conditions and thermal cycling, and all of which are relaively hefty bolts/nuts.
Ive also found it useful to buy a 'geared' box end wrench and a really high quality combination wrench if you use a specific bolt size often. For example, my MB has mostly 13mm bolts/nuts, so I got a geared box wrench and a really nice reular combo wrench in that size, and they have proven to be super-valuable more times than I care to count... I still use my k-mart 6-point 13mm socket though!
JMH