It sucks that none of these companies seem to be wanting to make 3 stream dual band wiifi adapters
802.11ac uses multiple 433.3 mbit spatial streams, each having around a 50% performance overhead, thus a top real world performance of about 200-216mbit/s per stream.
A 3 stream 802.11ac card can offer about 600-650mbit/s of real world performance if multiple connections are made (e.g., downloading from a local FTP server using a download accelerator such as downthemall).
the asus ac68 still seems to be the only 3 stream 802.11ac wifi adapter and due to the lack of competition, it is overpriced, and has driver issues.