I bought this one which ends up effectively having 6 10g ports since one is lost in uplink to my 1gb switch for older stuff - in terms of $ per 10gE port, it's pretty similar to the Asus that is linked above (~$100): https://www.amazon.com/NETGEAR-ProSAFE-10-Gigabit-Ethernet-XS708E-200NES/dp/B01GTWPTJY/ref=sr_1_1?ie=UTF8&qid=1498242510&sr=8-1&keywords=xs708e

I dunno how the performance is on that Asus card, but I've also always found it worthwhile to just get an X540-type card since it has great driver support in pretty much every OS and really decent performance (and iSCSI offload if you care about that) - https://www.amazon.com/Intel-Ethernet-Converged-Network-Adapter/dp/B00BGTTIUC/ref=sr_1_4?ie=UTF8&qid=1498242608&sr=8-4&keywords=x540-t2

@Vitaliy_Kisilev That's not crazy, though I'm OK with keeping things copper. Another option if you're going to be running all new cable would be to look at used infiniband cards and switches... though it can be difficult to find one with an ethernet port to hook into an existing network. Most people seem to end up using a PC as a gateway.