I know what you're talking about, it's just that headphones of any kind can't replicate the range of a sub because of the type of drivers that headphones use. That's a scientific fact because headphones can't have subs. I'm not saying 5.1 headphones can't sound good, I would just prefer having a really nice sub. I also have the room and don't have much of a restriction on noise levels, so I prefer to have the rumble of a true subwoofer for my home theater. Which is another thing headphones can't really simulate.
For the most part, you're talking to a guy who actually prefers headphones for everything
except for home theater. I'm a member of the head-fi forums. I take my music listening very seriously, so I use Beyerdynamic headphones at the moment until I can afford some nice sennheisers. They're hooked up to my PC through a DAC/Amplifier. I might possibly get some AKGs but I'll have to listen to them first. I know what headphones can do and also, just as importantly, what they can't.