I recently built a 17 disk NAS in a 12 part series. If you like gadgets and technology, I highly recommend checking it out.
One of the main features is 10Gbit ethernet. The motherboard I chose had two 10Gbit Ethernet ports built-in. I did need a 10Gbit NIC for my main workstation though. The on-board nic is an Intel X540-T2. This is a very popular 10GBit nic and I bought the stand-alone version used on eBay for $99 shipped.
Intel X540-T2
As I am only using 10Gbit for my workstation to my NAS (Network Attached Storage), I don't need a 10Gbit switch. I have a 24 port PPOE 1GBit switch that my entire house is wired into. In my configuration, I am using a 10Gbit port to go directly to my NAS and 1GBit port on both my workstation and NAS that both go into the main switch.
In a way, you could see the direct 10Gbit connection between the workstation and the NAS similar to a VLAN or dedicated network. It just saves me from having to buy a 10Gbit switch until I need more than two devices using 10Gbit.
While 10Gbit network cards are becoming cheaper and more commonplace, switches are not as quickly. They still cost a lot and have a very limited selection.
The Intel X540-T2 costs around $200 new and $100 used. They run really hot though and I ended up having problems with mine. I ended up switching to the ASUS XG-C100C 10G Adapter which is $97 brand new and runs cooler but only has one 10G port. It is important to find an adapter that has really good support on all platforms, both of these cards do.
ASUS XG-C100C 10G
Either card is a good option, but after my experience, I believe the Asus is a better option. The Intel was by far the hottest component in my system, even more than my dual Nvidia GPUs. The ASUS is smaller and a lot cooler and works like a champ.
Both options allow you to easily upgrade to 10G cheap between a workstation and server/NAS. Even installing 10G to all your computers is only a fraction of the price it was a few years ago. You can find some reasonably priced 5 or 8 port 10Gbit switches if you want to upgrade multiple machines.
There isn't a big difference with 1GBit and 10Gbit for most users unless you have a NAS or commonly move large files between machines. Most applications won't see a real-world performance with 10G. With a NAS though, the difference is huge, typically 300-1000% faster.
All images are from Amazon product pages