Basically I want to be able to attach USB 3.0 external portable hard drives to my network and maintain at least gigabit speeds.

I can think of four ways to do this, two of which I know exist:

1) NAS - get an NAS which features USB 3.0 and gigabit

2) Gigabit router with a USB 3.0 port

and I want to know if these two exist:

3) gigabit switch (multiple gigabit ports) with at least one USB 3.0 port

4) USB 3.0 to gigabit adapter

The gigabit adapter would be similar to this: http://www.addonics.com/products/nas30u2.php except that that is only USB 2.0 so it is not true gigabit, as gigabit is 125MBps but USB 2.0 is only 60MBps, so that adapter only has a maximum transfer speed of 60MBps and the "gigabit" is practically useless.