Hey, well i have a 5200+ on a MS2-SLI ASUS board, and i actually bought mine, so i had to overclock via Ntune, and i got a pretty good little overclock...
Stock was as you know 2.7ghz
I got mine up to 3.013ghz on stock voltages, on bumping up the FSB.
So my Ram was boosted from 800mhz stock to 884, on kingston value ram

. I had timings of 5-5-5-18, but i later changed it to all 6's becuase wen i ran prime95, it can with an error, but its ok, i hardly could tell the difference...
I had to also put my multiplier down from 5x to 4x. for stability.
this is all done with a program, so if you are doing this from BIOS, you will get a little better results, if you don't raise the FSB, but you just raise you cpu clock, you can get to 3.100 on stock voltages, but that is only you clock, and you would have to raise the voltages to go beyond that, you could get up to about 3.3ghz with voltage increases, i wouldn't go any higher than that...
If you are planning on overclocking higher than 3.0, then you MUST get an after market fan...My 5200+ runs on prime95 after an hour of 100% useage, at 59c, with stock fan and stock thermal compound. Max for this cpu is 65c...