1.63 volt on the GTX 570? I'm hoping you mean 1.063.
Also, one of the reasons that reference cards are recommended for SLI and Crossfire, is that they will have an easier time to get fresh air compared to most aftermarket solutions whom just whip the air around and they'd thus be cannibalising on the hot air instead of exhausting it in the back; Even with good air flow, that still happens.
The top air will be slightly more forced no matter how you set it up in air cooling; it also is the one where you plug the monitor(s) into, adding heat.
Either way, great to still see pictures of LGA1366