you don’t, at least with the apu2 (but I believe it is the same for the apu 4), as you can boot from any storage device, including a regular sata hard disk, which you can have if you mod the case or buy an alternative case.
Edit: I forgot to mention that those machines have two alternative intel ethernet cards, either the i210 or i211. Contrary to what the name would imply, the 210 is superior with 4 queues instead of 2 for the 211. This means that in certain situations you might have a bottle-neck and a slower traffic with the latter. I can attest that the 210 is a near gigabit speed with IPFire, if I do not use the intrusion prevention system.