505 is pretty high...
50-55 C is nothing to worry about.
The first question about what's up is for others to answer. Why should the mobo and the new chipset rise the temperature with 20 degrees? Maybe there was something strange with your former figures (30-35 C) as this seems pretty low to me unless you have a lot of noisy fans.
For comparision my Athloon XP 1600+ (never idling - always working at 100%) runs at 55 C. Then it's put inside a box that is put inside an office box and then the office box is (except of the front with the hinged door) is inside a kind of cabinet. This arrangement gives me a nearly totally noiseless environment, and a temperature slightly higher than average.