If you are worried about a high print quality then I would shell out the extra dough for the reinforcing kit. The more rigid you can make the frame and the areas that move back and forth the better your parts will turn out. If the extruder can wiggle around due to a weak base/frame then the parts are going to show that. Also, when homing things like the Z axis, you are going to want everything to stay put so that you wont have to continually home it and you will have that added peace of mind knowing that your Z axis is within a certain distance no matter where it is at on the heatbed. I cant see you having that peace of mind with a sloppy frame that moves and flexes.
