« on: May 26, 2013, 08:39:20 PM »
No, you're not too hasty to be thinking about full-frame; they're not any more difficult to use than APS-C (in many ways they're easier - more controls are directly accessible from the exterior of the camera without having to mess around with menus, for instance) and in the case of the 6D it's not that much bigger. If you're new to dslrs I don't think there's any reason why you need to learn via an APS-C before moving "up". If you can afford it, and if their advantages suit your needs, go for it.
Based on a glance at your photos, I think you likely would benefit from the 6D. In low light where you can't or don't want to use a flash, but will need higher ISOs, the 6D will give you obviously superior performance to the 600D (or any other APS-C camera, esp. current Canon models) both in terms of noise and accuracy of focus. In many such situations - interiors of buildings, esp. churches - you will also benefit from the near-silent shutter of the 6D. Also, you can more easily isolate your subject/blur backgrounds with the 6D. If those three things don't matter much to you, you might as well stay with the 600D (or forget DSLRs altogether and go Micro 4/3 etc.).
If if I were you (but of course I'm not) I would take option 1. I trust you realize, in comparing the lenses you mention, that thanks to the APS-C crop factor the 24-105 on the 6D is a bit wider but quite a bit less long than the 18-135 you mention (the equivalent on FF to that lens on APS-C would be c. 28-216). If you go FF you may want to add something longer at some point, such as a 70-300.
And yes, you'll want some accessories, but - at the risk of getting laughed off the internet - I would suggest starting light, with a good RAW converter such as lightroom (if you're going to go to the expense of buying a dslr it would be a shame if you didn't shoot RAW) and later figure out what else you need. (For instance, depending on where you go and what you shoot, a tripod could simply be a nuisance, especially if you have lenses with good IS and know how to hold a camera steady.)