PCI Adapter for RT-N56U

I am looking at a wireless NIC (Over PCI) and I plan to use a 5GHz band as the N56U router supports it, it will allow my network to be on its own private network kind of.
But I need it to work with Linux also, I currently run Ubuntu but I also run Arch Linux at times, depending on what I can be bothered with at the time.
I was looking at this, I do feel it is a bit expensive http://www.cclonline.com/product/172574/ARCHER-T9E/Wireless-Adapters/TP-Link-Archer-T9E-AC1900-Wireless-PCI-Express-Adapter/NET2134/

Is this over priced and too much for the router? Or will I be able to reach near the target 1.3 speed on 5Ghz.