Sapim supers are some of the lightest and most aggressively butted spokes on the market. If you're after stiffness, they shouldn't really be considered. Just putting that out there.

Spoke count is probably affecting your perception of stiffness the most, your Boyds are fairly under spoked for your weight/power.

Whatever you get, you need more spokes, and not necessarily 600 dollar hubs.

I can't imagine dropping 1200 dollars on alloy wheels, especially if they aren't telling me any power data.