I'm also 6'4 and have spent the past couple months looking for a solid two person tent that I could share with one other person. I use trekking poles, so I've been looking at some of the boutique tent makers that are very popular on these (and other) forums. I still haven't made my purchase yet, but here are some observations I've made in my search.
The LightHeart Solo looked really cool to me. The floors are long, but it doesn't look like there would be enough interior space for me to be comfortable. The walls are pretty steep and slope medially, I doubt that I could lay on by back without my head or my giant feet hitting the walls. And it looks like sitting up would be impossible with two people in the tent, considering that I have a relatively tall sleeping pad (Exped). The LightHeart SoLong looks like it could address some of these issues, but the medial slope to the walls doesn't really appeal to me.
ZPacks tents are awesome looking, but the cost alone is enough to turn me away... perhaps when I get more serious about backpacking, but not now. I also don't like the entry/exit situation for their tents.
GoLite tents seem decent, but the placement of the trekking poles is a dealbreaker for me. Also, they only have one door, which I don't like.
TarpTent makes some tents that I've heard other tall folks praise, and TarpTent has a great reputation. Specifically, the StratoSpire 2 may be worth checking out for you. It has a lot of space and has more vertical walls than the LightHeart tents, allowing for a good amount of interior space. It's also a doublewall tent, which is nice to have. The Double Rainbow is also very popular, and has some solid design features. The shape is pretty neat, too.
The Six Moon Designs Lunar Duo is also very popular, and could be a solid choice for you. It's a little longer and wider than the two TarpTent options I mentioned, and thanks to the ceiling design/shape it's supposedly incredibly spacious. I've heard many great things about this tent.
For my purposes, I think that I will end up getting the Lunar Duo as opposed to one of the TarpTent options. The Lunar Duo is a little longer and wider, which is really appealing to me. I also like that it's design maximizes the usable interior space, and I won't have to worry about my feet or head brushing against the walls. I could probably go with either of the TarpTent options and be just as happy, but the extra width/length of the Lunar Duo provides me a little more piece of mind.
Let me know what you end up getting, it could help me make my own decision!