Awesome reply -- thank you. I'm not sure if someone else will be as OCD as I am, but if there is someone else out there, at least I'll have asked some questions. 
As some background for people wondering where these questions are coming from, I don't have my 190 XDB with me because it was too heavy to go in checked baggage. I was already at 51.5 pounds without the tripod, so tripod + head would have easily pushed me over. So now that I'm in Europe for six months without a tripod, I'm freaking out a bit.
So, now for responses to responses.
For long exposures you absolutely need stability.... However I would guess that if you pushed the center column down completely and locked all the twist locks - both the legs and center column - really tight the 1-Series Gitzo might be sufficient.
Tough one. If I had a car then hiking I'd bring the systematic. If I was carrying all day I'd bring the Benro traveler. If I was shooting night shots I'd use the systematic. Most of my night shots are urban; I use film Leica rangefinders and at night a 50mm/f1.0 Noctilux. You need super stability to get the effect you want with that kind of glass.
Given that you're mostly doing long exposures I think I'd get the 2-series. Actually I'd also suggest the Benro C-358 M8/C3580T which
you can get on Amazon for $385
(it used to be $211!)
and on eBay for $316
. Check out the specs at the Chinese eBay sellers.
Based on the first two, which the last then summarizes, it sounds like what I want is a Gitzo 2-series traveller, which doesn't exist outside of a kit (whose head I don't like). So...
1) Is the Benro C-268 really a 2-series copy? Its specs are kind of in-between the 1541T and the 2541.
2) If I do want a 2-series Traveler without head, does anyone make that tripod?
3) Relevant to this thread, can the C-268 function as a 2-series Traveler, or is the 2541 still going to be a bit sturdier than these legs?
Yes. You're paying for the brand name but then I do the same. Leica costs a fortune but when you see the B&W silver gelatin prints it's all worth it. However I also go for what works and this Benro C2680T is a better solution for me than the 1541T. I have a couple of Voigtlander lenses as well.

In your opinion, based on the entire tripod and its merits -- is the cost difference between the 1541T and the C-268 entirely due to the name/heritage of the Gitzo? In other words, is there anything relevant to photography that one sacrifices in buying a Benro? (If not, what makes it so much cheaper?)
I just used the 1541T again after several months to do the vibration thing you asked in (1) and those leg locks are horrible.
What makes them horrible?
Benro's US distributor doesn't sell the full range of Benro tripods and seems to want to sell the least interesting stuff actually. To get a twist-lock model make sure there's a T in the model number.
Ah, thanks. I know you bought on Ebay; it seems like Holga Camera sells the C-268T (without head, and ships to Germany!). Any knowledge of their reputation? (As in, did you consider seller reputations before buying on Ebay, deliberating avoiding Holga?)
If you're 5ft 10in+ look at the Feisols; lots of taller people really like them and they're the only solution for big guys. I'm 5ft 8in so Benro/Gitzo are fine for me. Another thing is that because the Benro is a Gitzo copy some parts are interchangeable...
I'm short (5'6"), so the Benro should work well. My 190 XDB requires me to lean a bit, but it's not a lot. I think the 1541T might be a bit short; the C-268T looks pretty on-par.
Turning to ballheads for a moment I think the Markins Q3T is a fine ballhead.... However recently I was dismayed to find that it can't handle my Nikon 17-55/2.8 zoom lens....
The one advantage of the 1542T is that ballhead diameter isn't an issue any more; so if I had the 1542T I could solve my Q3T problem by selling it and getting a Markins Q10.
Well, uh-oh. I have the Canon 17-55, which I realize is a bit lighter than the Nikon, but how bad is the action of the ball with this type (i.e. front-heavy) of a lens? If the body were heavier, would this help, or do you already balance your setup regardless of how heavy it is?
As for the 1542T, having the ball extend beyond the legs does negate the ball diameter question but it also means that the tripod head would extend the overall length of the tripod. Would, say, an M10 be too heavy for the 1542T? I had figured if I went with an M10, I'd go with a 2-series legs.
Since we're on the subject of the Q3t, what is this about the Q3t's panning base not locking? I typically use a remote (now, anyhow hehe) and MLU with a 2 second delay, but does the ability to rotate allow for increased vibrations at all?
Thanks again for your help. Really appreciate the insight. Now that I'm actually likely to buy a decent setup, I'm trying to make sure it's the right one (and really, I am hoping there's "a" right one!)