Also keep in mind, the FCX and 6610/6650 platforms are NOT the same CPU/architecture as the 6430/6450 and 7xxx series lines. The 6430, 6450, and at minimum the 7450 and lower 7k switches are all ARM-based CPUs, not whatever the others use (PowerPC? I can't remember) so they suck a LOT less power just by default.
I agree that you're probably SOL on lower-power with BGP through the ICX line, but just on the off-chance you haven't, have you actually checked out the noise on a 7450? I've had them running on my desk for pre-deployment configuring and they're not really that loud, even the PoE ones. The FCXs and the 6610s are screamers (ESPECIALLY the PoE ones), but I haven't found the 7450s that terrible.
Of course, I haven't had one permanently parked 10 feet from my chair either, so yeah.