You might perceive the beer to be a bit thin bodied (or watery) for what you're expecting. But don't worry about it--you made a session-strength beer. A lot of us like them. In future batches, you may want to limit the water so you end up with the targeted OG and a beer that has the characteristics (body, taste, mouthfeel, etc) that you're looking for.
I often made that mistake early in my brewing days with extract kits under the mistaken belief that I could stretch a 5 gallon kit into a 6 gallon batch. With kits, adding water to make "more beer" does not equal "better beer." In fact, the opposite is true.
The solution is simple: Add more sugars (increase gravity points) or Reduce the volume by boiling offf or not adding water.
A quick fix could be a trip to the LHBS and get two pounds of DME (44-45 points per pound), dissolve it in no more than 0.8 gallons, boil it x 10 minutes, cover and cool it down to 70 F, and then transfer it aseptically into your fermenter to add more gravity to the existing volume.
SG 1.041 (250 points / 6 gallons)
SG 1.050 (250 points / 5 gallons)
SG 1.050 (300 points / 6 gallons) or (340 points / 6.8 gallons)