KitGuru tried the Asus PCE-AC88 Dual-Band AC3100 Desktop Wireless Adapter
A quote from the article:
Asus is now the first company to bring a 4×4 802.11ac Ethernet adapter to market, in the form of the dual-band PCE-AC88. A small PCI-Express card, it's intended for use in desktop PCs and is capable of the same fast 802.11ac performance that's possible from 4×4 routers, with even faster speeds for any router that support a 1024-QAM configuration.Asus PCE-AC88 Dual-Band AC3100 Desktop Wireless Adapter Review @ KitGuru