for the cpu, the oc is on the low side. the problem will be the motherboard for sure, with out even needing to look in the manual. im pretty sure your dont have many options to work with. G31 does support up to a native 333fsb, im sure the cpu can do that for sure. if you want to get that far your need to manually set the dram speed to a 1:1 ratio which would be the lower dram speed you can choose. without knowing the other options the board offers should you try for 333mhz fsb you may oc the ram to far and the computer wont boot. if you stick with a 1:1 ratio that would put the dram speed inline with the fsb, giving you a ram speed of DDR2-667.
without knowing the cooler your have or the type/model ram you have it is hard to say. just how much farther it would go if you had more options in the bios for fsb/voltage controls. my safe bet is the 1:1 with fsb at 333mhz for the cpu/ram, would be a nice boost cpu wise to help the system seem "new". while it wont blow the doors down, if all your doing is sending im's and facebooking, you dont need a six core cpu. while it is a good deal at MC for the cpu/mobo, do you really need it?