FYI, you can buy the best components available and have the adjustments go out as most times new cables break in etc. If you bought a new bike, it may require a little fine tuning of the rear derailleur cable. Most people don't know this then think it's just that the components are low end when in reality, they just may need readjusting. Very easy 'do it yourself" if you are any kind of mechanical. Check out sheldonbrown.com or Parktool.com for instruction.
Might want to keep an eye on the brake cables sometime down the road too. Wheel spoke tension is another important issue at your size. after 200 miles or so, the spokes lose tension and should need to be readjusted or expect some broken spokes somewhere down the road.