With every room being so different, I think the subwoofer crawl is your best best. No, the EP800 isn't overkill, but like you suggest, having two subs may offer smoother performance over a wider range of seats.
I personally ended up with four EP800s, but not because one or two weren't cutting it, but just because I planned on having them fill a larger space eventually, and four seems to be the magic number people talk about as far as smoothing out the bass response. Not that the final room they'll be in won't be a problem for placement of four subs. Wish me luck on that.
As for horizontal vs. vertical, go with whatever you think works best for where you want to place it. I ended up with two horizontal and two vertical based on where I think they'll end up in the basement, but in the current room, they're all standing vertically. Instead of on feet, they're on Auralex SubDude HD platforms. I'll experiment with both orientations when I move my system, but I'm more than satisfied with them all being vertical in the current room. Obviously, vertical has a smaller footprint, but horizontal will let me place one one a concrete ledge I have behind my screen as well as under a table at the rear of the room, if I end up going that route. Either way, I think it only really matters if you're going to use the feet, which I'm not. You can always find a way to face the holes for the feet in the least visible direction.
