Tiger direct has i7 4770k at 299 right now and not sure for how long. Both are great boards but bang for the buck I would think the M6E would be the best bet. M6F has the supreme audio where as the extreme does not. just my opinion. its all what you want to spend and what you will want it to do.
Maximus XI Formula, I9-9900k, Phantex Evolove X, Seasonic Titanium 850W, Custom loop PE360+SE360 Rad, G.Skill Trident Z F4-3200C14 32g, Nvidia Reference RTX 2080 TI, Samsung 970 EVO Plus 1Tb, Windows 11