Doesn't AC have better range and/or better signal through walls, etc? That was why I thought about going to AC, so I could get better all house coverage.
That's really going to come down to the antennas more than the standard(b,n,ac,whatever)
AC routers *can* support up to 8 seperate antennas running at 400mbps apiece, but I haven't seen one with more than 4 antennas. The best "n" routers have 3-4 antennas currently, so your range and structure penetration right now isn't going to be much different than an equivalent "n" router.
Also, ac exclusively uses the 5ghz band, while n used both 5ghz and 2.4ghz. The 5ghz band is faster, but doesn't penetrate through walls/structures as well as 2.4 ghz, it has a shorter effective range, however 2.4ghz is used by a lot of different types of devices, so there's more interference on that band, so real-world usage you'll generally get a cleaner signal with 5ghz, but it may not travel quite as far as 2.4ghz.
and lastly, the ac standard has what is called "beamforming". Up until this point, routers just broadcasted a signal out in all directions, so you always wanted your router in a centralized location in your home. What "beamforming" does is the ac router detects the positioning of connected wireless devices and attempts to focus the signal to transmit stronger in that direction.
I honestly have no clue how well beamforming works, I've never used an AC router, but the idea behind it sounds good.
so tl;dr, ac is faster, but you probably aren't going to see any better range than from an equivalent quality older "n" router