All high end MB's should have 10GbE, or at least one model in each line. NAS's should also sport one of these.
That said, you can get a Mellanox ConnectX-2 10Gb card for ~$55 (mine also included the SFP+ cable which is expensive on its own). This is a cheap way to get a point-to-point 10Gb connection for use between workstation and a file server. You don't need a switch to go between two machines, so you can avoid what is usually the biggest single expense in a 10Gb network. I am using these cards for a SAN and the bandwidth is much higher than on 1Gb, but even with these cards, and jumbo frames enabled, I only see around 3Gb/sec using SMB and a bit higher using iSCSI. On Windows 2012 R2, SMB(3.02) has absolutely terrible actual performance compared to iSCSI though, and this matters when using things like PLEX media server, which transcodes and stores chunks of video to stream while also pulling the full source data over the same link, meaning a single HD stream can use up to 150Mb/s of bandwidth to/from your SAN.
Lastly, something to be aware of that matters with 10Gb is that the interrupt processing can be detrimental to attaining high throughput. With SMB(3) on Win2012, the use of RDMA can help dramatically with this, but the X-2 cards don't (officially)support RDMA. They do have interrupt coalescing and several settings to adjust but you can't keep up with data flow unless you have a decent CPU to go with it. I'd recommend no less than a 3Ghz quad core chip on anything with 10Gb, and don't forget you need a PCI 2.0 x8 slot to put it in. If you arent running on a platform like X99 with a 5960, you can run short of PCI lanes once you have RAID controller(s) and possibly a video card in play.