I hear you on that...Regardless if you go with the x540, x550, or the x710, they are all 10Gbe cards. The x540/x550 use RJ45 so that would use cat6a cables. The x710 uses SFP+ so the ports will either need DAC (Twinax) cables or you can insert a modular transceiver to make it any type of port you want. The reason I recommend SFP+ is the price of a 10Gb SFP+ switch is cheaper than a 10Gb RJ45 switch in most cases. You can also make the port any type of connection you need using a pluggable transceiver.
Even if you are just direct attaching the two devices without a switch, DAC cables cost about $11 each and the SFP+ 10gig cards are usually cheaper than the 10gig RJ45 cards and you aren't tied to one specific connector type. If you do plan on upgrading in the future to a 10Gb switch, you will also be paying less for an SFP+ capable switch but even so, with SFP+ transceivers, you can use any type of connector you want. Not so much with RJ45.