I'd like to think I'm a little qualified to answer this question...I have 9 torque wrenches and about $45k of tools sitting in the basement and garage (being an ex-technician of 7+ years helped acquire a few tools).
While the quality of a Snap-On, Mac or Matco tool is generally higher than consumer-grade tools, I would not recommend buying a Snap-On, Mac or Matco torque wrench via eBay.
The chances of it being out of calibration are simply too great, and to have the wrenches calibrated costs over $100.
For my weekend projects, I use a Craftsman torque wrench. I have the 20-120lb model, 1/2" drive and I have a 3/8" drive model as well. Both are close enough for the weekend warrior and will withstand weekend-type work loads. I use them for torquing wheel lug nuts, and things like that - works perfectly.
If you were a pro-wrench and were using your torque wrench every day, or were torquing critical components like bearing caps and transmission components, then I'd say to get the Snap-On, Mac or Matco. But for things like lug nut torque, brake caliper torque, etc., the Craftsman will be more than adequate.
Oh, and one last thing - many newer cars have "stretch to torque" values. You torque the fastener to a certain value, then you use an angle guage to torque it a certain # of degrees past the first torque value...it stretches the bolt.
