Luckily the ones I have behave just like modern Ethernet adapters, in that they seem to support auto negotiation, so all you need is two cards, and a cable to do 10Gbps speeds.
Obviously as mentioned earlier your disks need to be able to keep up to fully saturate that link, 1200MB/sec approx is one 10Gbps link can handle. a DVD image in a few seconds.
Setting up two 10GB ram-disks each end will be a good way of saturating the link, as then your pretty limited only by the cable and the system bus speed.
Also yes, I did look at 10GBASE-T but those cards were like £400+ each. and switches were like over £1000+. I saw many cheap (£100) CX4 cards available on eBay, and I also spied on the Brocade CX4 switch which had 4 CX4 ports and 48 standard gigabit ports as well, for about £180, plus its managed so its possible to team up some of the gigabit ports.
Id say the advantage of CX4 is its pretty cheap and it justifies upgrading to it, since I can't fit 10X gigabit cards in a single 8x PCIe slot.
Fiber to me seems very delicate although it can go potentially many KM, I think I just like the robustness of copper for now.