Thanks for all the help so far, everyone! Much appreciated.
I have to say, the RRS pods look pretty awesome. The lighter weight/stronger design is definitely a big draw, and I figure at some point I'll probably pick one up. My big purchase for this year will be the EF 600mm f/4 L IS II lens, which is why I am looking for a good tripod in the first place. I would love to get the TVS-34L, but it is quite a bit more expensive than what I was looking to spend.
I have a rather large chunk of Amazon Prime points saved up, which will give me a pretty hefty discount. The Gitzo tripods there are all between $720 and $800, so I'll end up spending no more than $650 (and possibly around $550, which is just what I was hoping to spend) buying a tripod there. If Amazon sold RRS tripods, I'd probably pick one up, but seeing as they do not, I think I am going to go with one of the Gitzo tripods.
I've looked into the GT3542XLS, and that actually seems like a pretty nice tripod. It reaches a maximum height of over 78", which is more than good enough for my 73" height. Actually, I think my eye level is more like 68", but someone mentioned the nice ability of being able to level the tripod on uneven ground. I think I could definitely use that capability for my landscape photography. The other Gitzo 'pods, the GT3535LS and GT3542LS, are around 58" high, 20" shorter than the XLS. They would probably work fine for my eye level, without the extra leveling versatility that the XSL offers.
I'd also read some reviews of the XLS, and it sounds like a solid tripod. When it comes to stability, many reviews recommend not fully extending the last leg section for improved stability. Seeing as I would either not extend the fourth section all the way, or maybe only partially extend it, I think stability should be fine. It seems the majority of professional photographers I follow, most of whom use the 600mm and 800mm lenses most of the time, use the GT3532LS, which is only rated for 400mm lenses. I think from a weight handling standpoint the XLS will still be fine.
I guess the only drawback I see with the XLS vs. the LS is its collapsed height. It is over 28" long collapsed, where as the LS is a little over 22" long. If I wanted to travel with the tripod, a 22" one would fit in a carry-on, where as a 28" one would not. At the moment that is the last thing I guess I need to decide on.