+1 ebay x520 cards. My entire 10g sfp+ home network runs on a bunch of x520s, fs.com DACs/AOCs, Mikrotik switches, and an old desktop running FreeBSD with a few x520s in it as the core router. Very very cheap to assemble and has been absolutely bulletproof. IME at this point in time the ixgbe driver is extremely stable.

x520s with full-height brackets do exist (I have a box full of them), but you may pay like $3-5/ea more than the more common lo-pro bracket ones. If you're willing to pop the bracket off, you can also find full-height brackets standalone and install your own.

Also, in general: in my experience avoiding 10gbe rj45 is very worthwhile. More expensive, more power consumption, more heat generation. If you can stick a sfp+ card in something, do it. IMO 10gbe rj45 is only worthwhile when you've got a device that supports it but can't easily take a pcie nic, like some intel NUCs.

sfp+ is clearly cheaper, and less heat/power, but I've got cat5e in the walls and between my house and detached garage, so I've got to use 10g-baseT to get between the garage and the house, and up to my office from the basement. At my two network closet areas, I use sfp+ for servers.

I think my muni fiber install happening this week might have a 10G-baseT handoff, and I've got a port for that open on my switch in the garage. If that works out, that will be neat, but I'll need to upgrade some more stuff to make full use of that.