I prefer BuyDig.com and B&H. Both of the sources are reputable, reliable and fast. The prices might not be the very BEST you can get, but you will be assured of quality service and in case anything goes wrong, you can rely on thest suppliers to accomodate your requirements without hassle.
If you are a DSLR beginner, I suggest you go for the kit with the 18-55mm lens. Play around with the combo till you get comfortable, before you sink anything into the camera system. Unless you are really strapped for money and absolutely need a tele zoom, stay away from the 75-300mm. Get a chaper mid-range zoom (35-135mm, 28-135mm etc) used on ebay or other places. If you are really interested in telephoto, save up for the 70-200 (you can either choose the f2.8 or the f4, both with and without stabilization) or you can get the 70-300 DO.
My advice again, (coming from bitter experience and the endless money suckers my two passiosn are - MINI and Canon 20D
), don't invest anymore till you get comfortable and confident with the system.
