Unfortunately, they're right. If you go 1 step up or down on a sidewall you won't notice much difference. Using this:
http://www.csgnetwork.com/tireinfo4calc.html
If you were travelling 65 on 265/65's your speedo would read 62.85mph on the 265/70's. If it's an issue to you, that's understandable. I'm not crazy about going + / - myself either.
I've heard the Rugged Trail are crap, although they do look similar to the AT, they are still an H/T tire. I'd look at a Nitto Terra or the Pirelli ATR, or even the Goodyear Fortera (which I hear actually has proven to be a pretty good tire for an occasional trip down the trails.
There's always the ever-popular Revo as well. I bit the bullet and had to see what all the hype was about and purchased a set of 265/65/17 and they've done everything I had expected... but I don't do serious off-roading. We had a 14" of snow a month ago- no problem... also a few trips to an offroad park proved no problem either... but I wasn't in a bog either