I'm running almost all modern wheelsets.
Alex ACE-19, Mavic Cosmic & Ksyrium Elites, Bontrager SSR Aeros, Shimano WHRS-10, Ultegras, & Hope/Ambrosio.
The exception is a set of Campy Vento deep-V's, and no one yet cares if they're not light, or modern.

Only the Ksyrium Elites and Hope Tech/Ambrosio (tubulars) are that light.

Frankly, outside the Hopes and the Elites, the rest are all about the same and I don't notice weight differences.

Used:
Ksyriums (not Equipes)
Aksiums aren't that far off
Fulcrums
Bontrager
Eastons
Sometimes, a set of Zipps comes up, almost always tubulars.
Tons of others, watch your load limits.

New:
Vuelta's
Nuevations
PBK always has some on sale
Fulcrums
Bontrager
Not sure if $500 will get you the weight you want.