I had both the 680i & 780i. I can't find any pictures of the 680i but here's a pic of my 780i. I replaced the stock Northbridge Fan with a Hi-Speed 60mm fan from an old AthlonXP Heatsink. Newegg sells 60mm fans, the higher the cfm rating the better. I also added a 40mm fan to the Mosfet Heatsink. A week or 2 later I added another 40mm fan to the Mosfet Heatsink (and I flipped the mosfet fans so that they were blowing in the other direction). But I didn't take a picture.
With these fan mods my NB Temp dropped from the 60-70 range down to the 40-50 range.