Maybe something like the PC Engines apu2? http://www.pcengines.ch/apu2.htm
x86, can run OpenWRT.
x86, can run OpenWRT.
At one point I had an 802.11n card in my older ALIX2D router, but there were stability and performance issues so now I always use a separate access point, most recently a Unifi AC-PRO which has some quirks but works well in general.
I've been happy enough with the x86 routing strategy that when it came time to replace my older Cisco 100mbps switch, I decided to do that with x86 hardware as well. All of the smaller/cheaper gigabit switches either didn't support VLANs, made way too much heat, or had reliability issues, and the ones that were suitable were quite expensive and had reliability issues of their own.
So, I found a Supermicro Atom C2000 board (A1SRM-LN7F[1]) on sale for $90, which has 7 Intel NIC gigabit ports built-in and supports ECC ram. I put it in a Supermicro 1U[2] enclosure along with an Intel PCIe 4x gigabit NIC, for a total of 11 gigabit ports on the switch. I installed Debian on it and set up open-vswitch, which worked but was soon replaced by "vlan-aware" Linux bridging.
It's easily capable of switching gigabit traffic between multiple machines at the same time, ping shows an average latency of 0.310ms, has very low power usage and makes very little heat.
Note that those C2000 Atoms do have a "sudden death" hardware flaw, but Supermicro should have fixed it on more recent inventory, and they will send a "patched" board to replace any that are affected before they fail. The Atom C3000 doesn't have that issue, but I don't think Supermicro (or anyone, really) make any C3000 boards with that many built-in gigabit ports.
[1] http://www.supermicro.com/products/motherboard/Atom/X10/A1SR...
[2] http://www.supermicro.com/products/chassis/1U/510/SC510T-203...
Later today (if all goes well) I'll be adding wifi to it!