Just looking for others opinions and hopefully experience on wether an upgrade from the 40d to a 70d would be a worthwhile thing to do.

Currently the main consideration for it is an upcoming trip to Europe later in the year.

Currently the kit consists of the 40d, Sigma 17-70 DC HSM OS, Canon 50 f/1.8, 70-300 IS, as well as a Canon 430 EX flash.

The majority of shots that I take are landscape, and would probably be the same on the trip, apart from some indoor stuff like cathedrals, etc that you often find in that part of the world. A lot of my pics are usually taken on 4wd trips away, so quite often there aren't too many other people around to take pictures of, and there is just a lot of nothing, or not much.

My biggest issue is that there is nothing wrong with the 40d, so why upgrade it? It still performs perfectly fine, produces some pretty good shots, and I've never had an issue with it in the 6 or 7 years I've owned it.
But at the same time the advantages in low light that the 70d offers makes it an appealing upgrade. But then I think that well I've got the flash there, so is there really going to be that much gain to doing it, apart from the fact that I wouldn't need the flash in a lot of places with the 70d.

Sure I'd love to go to the 6d, but having to upgrade lens' and body all at the same time isn't so appealing right now, as great as it would be to have a 6d!

Have others gone through this conundrum and can offer some advice?