Both GPU & RSX need reflowing. I've seen this time and time again, console works until opened up. When you take the board out, it flexes and stresses the BGA connections. If they are already weakened from prolonged 'heat-soaking' and lack of ventilation, the actual lead balls used to solder the ICs become brittle & oxidised - eventually leading to YLOD.
60Gb boards - I'm guessing yours is either an SEM-001 or COK-002 - both used in the 60Gb PS3 (phatty) are prone to not only YLOD, but the main culprit is the Southbridge chipset (controls the audio/video output from GPU etc).
If you look carefully at the RSX & GPU on your board... at each corner of the chip you'll see (or SHOULD see) a solder connection right on the very corner. I use these to judge if whether or not to reflow the chip, as these 'corner tags' are the first to be ripped off by the PCB flexing.
Check them out, they're also on the southbridge chip (I'll try and find some pics to explain...)