For a home mechanic, two or three Harbor Freight click type wrenches are OK. They are cheap, "ball park" accurate, and any torque wrench is better than no torque wrench. They are certainly good enough. One wrench is inadequate for your tool box, since it can't handle the wide range of torque values you may encounter, and they are only accurate in the middle of their torque range, not at the extremes!
I would start with a 1/2 drive 150 or 175 ft lb unit, for wheel lugs and heavy suspension stuff. Then add a 3/8 drive 75 ft lb and 1/4 drive 200 INCH lb wrench. If you ever have to torque a really big bolt like a harmonic balancer bolt, rent a 3/4 drive tool from the auto parts store, because those suckers are expensive...
If you ever plan to turn pro, spend the extra $$$ now on a set of high quality tools, and get them calibrated at least every few years. In the aircraft industry they have to be calibrated annually.
Do NOT buy any wrench that does not have an audible and tactile "click!!!" - often you can't watch the display and reef on the bolt at the same time. You must be able to feel it reach the set limit. That digital wrench is pretty cool, but you have to either watch the lights or display, or listen for the beep, and in a noisy environment that may not be satisfactory.
John Davies
Spokane WA USA