I just notices some really interesting new devices in the Raspberry-PI-Segment with Gigabit LAN and USB3 just recently came out - it seems Gigabit-Ethernet has finally landed in the Raspberry-Pi-segment: It seems all of the devices can be purchased starting right now.
The first one:
1x Gigabit LAN
2x USB2.0
1x USB3.0
SD Card slot
with 1 GB RAM ~40$
with 2 GB RAM ~50$
with 4(!) GB RAM ~80$
(still needs a power supply unit + casing extra)
The second one:
http://www.orangepi.org/OrangePiOneplus/ (purchase link on top right links to Aliexpress)
1x Gigabit LAN
1x USB 2.0
SD Card Slot
with 1 GB RAM for ~20$ (!)
The third one:
http://www.orangepi.org/Orange%20Pi%20RK3399/
1x Gigabit LAN
4x USB 2.0
1x USB 3.0
WiFi-AC (2x2 MIMO 2.4+5)
mSATA + SD Card
...a lot more features
with 2GB RAM ~100$
All should have very good Linux open source support. And according to the documentation, it seems at least the roc-rk3328-cc has exceptional high AES-HW-accellerated OpenSSL throughput, which would make it an ideal VPN device.
Also all 3 of them have either HDMI or Displayport as well.
Disadvantage though: The devices still only have one LAN port and the cheaper ones do not have built-in WiFi. So some extra managed VLAN-capable 5 port switch for 20-30$ would be needed to attach to the LAN port and some USB-WiFi stick for 20-30$ - It might also be possible to use an USB3->LAN adapter to obtain a second LAN port.