Don't go for the house with the smoke, the cops are watching it ;-)
I've slowed the CPU clock down on my Q6600 GO to 3348Mhz and bumped up the memory speed to a third of that so it's better balanced, cooler with less voltage and faster. With the room at 28C and the CPU is running at 49C with cores running around 59C to 62C so no smoke...yet.
That one just made the 6000 RAC mark today and I'm expecting it will go higher over the next week or so. Hoping for it to break into the Top 100 Computers on the SETI site, but that might be wishful thinking.
So the two quads are well past the 10,000 RAC mark on their own and so I guess a total RAC of 12,000 to 13,000 may be sustainable.