I could do a 1RM of bench with 260, and when I started 5x5 I decided to go real light and get used to the routine. I started with 190 on bench and worked up to 245 nice and steady over a 3 month period. When I was done I did a 1RM with 290, I was happy, but wanted even more, I can't wait to bulk again. So if in doubt go lower, there is nothing wrong with taking it easy and building a good solid base with each exercise. I figured that I'd rather take it slow and keep those 5 pound gains coming every week than start right near my max effort and run out of gains after three weeks.