X5460 Overheating

[nootnoot1277]

Hey guys
(For my Lan Party PC) The mobo i just bought arrives (Nforce 780i sli) i'm going to put it with my x5460 and twin gtx 480 water-cooled setup. now my problem is that just before my previous board died (ms 7529) i was noticing that changing from the q6600 i used to run to the x5460 the cpu was running pretty warm at idle with a big ol scythe tower cooler on it (idr which one its the one that looks like an iron cross from the top) with 2 120mm fans on it, now this Xeon i bought because it had been modified so the lga 771 to 775 sticker thing had been sort of stuck to chip so you don't have to use adapters and that 2 notches had been ground out of the side meaning it could essentially go in any lga 775 board without modification to the socket bed (quite smart i must say) now i was watching doctor who for a few hours as this pc is a htpc when its not a lan party pc and it was fine mostly hovering around 54c if i remember rightly but then i tried to run intel burn in and it would do a few marks before boom the pc shuts its self down, i try again with the same result the chip would get to its safe point which i think is just over 80c and shutdown. i'm thinking of solving my problem by just watercooling the bastard with a 240mm rad but before i do i was wondering if anyone could think of any reason why this x5460 was running so insanely hot with a decently big scythe cooler on it. just thinking maybe something wrong with the coolers contact pipes or if its the cpu its self.
cheers guys and apologies for the article haha.