How many in your family? If you have 5 of you, at least myself, we would have "most" std 15 series rigs at or close to gvw BEFORE hooking up the trailer. Being as I actually have 6 of us, we were in the 1200-1300 lbs range total when my 4 kids were adult sized teens!
I have no doubt the ecoboost will tow a trailer of that size with the power specs I have seen. Frankly, it is too bad Ford and GM/dodge etal are not offering an equal motor in the 8 lug 25 series setups. Many like you, myself that tote 6-8K trailers with larger families, would find it to be a perfectly acceptable option! Yeah it will not be as fast per say up the hills etc.....but for many of us, the how fast one gets there is not as important as having the correct tow rig to do it safely. A 25 series WILL get you there in a potentially safer manner than a 15 series rig will! Its just too bad the smaller motor options seem to be going away! a 200/400 to a 250/500 power spec would be just fine for my applications. A 400/800 is way more than I generally need. Heck, even my 300/600 motor is more than ample!
Marty