Your lacking some info.
Your Games n Stuff PC......what OS is that running?
It's easy enough to get decent speeds from Xpenology's networking.
If your OS for games n stuff is Linux / BSD / Unix etc then bonding multiple cards can be the cheapest way to go (no switch needed if direct connecting)
else cheapest is to grab some old 10Gb Fibre cards, and a length of fibre cable should see you getting an easy 9.90 Gbits/sec
Way more than a bunch of HDD's raided together will give you.
Emulex 10GbE Virtual Fabric Adapters work perfectly, and can be found cheap on eBay... if your lucky they will come with transceivers.
Then all you need is a cheap LC to LC 50/125 cable to connect them together
if you need more speed, buy dual port cards and then bond both of those ports together
quick guide on how to bond gigabit cards here
http://xpenology.com/forum/viewtopic.php?f=2&t=2476
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