It not a video guy so take this with a grain of salt, I'd actually probably only get one of either the 17-40 or 24-105. Seeing as you already have a 50mm I'd probably say get the 17-40 now used maybe $500 or so which leaves you with $600 towards a 70-200, few more months of savings and you'll have the 70-200 used maybe $900ish.
You have a 50mm lens. Do you want wider, longer, or both? If you want wider or both, get the 17-40 and 24-105. If you want only longer, get the 70-200mm f/4L IS.
The IS on the 24-105 will be huge. There are plenty of videos out there showing its prowess. I think the 17-40 might be a touch redundant... and it a little soft for photos until it is stopped down to f/8 or so... I'm not sure about video, but usually the 17-40 is a stepping stone for people interested in L quality... but it isn't really a good L lens.
You can find the 24-105 for around $750... and then save up for the 70-200mm f/4L IS. I haven't used it... but it has a great reputation.
For video definately the 24-105 f/4 L IS ... coz it is a lot easier to do handheld video than a 17-40 which does not have IS (and it has too much barrell distortion for my liking) ... I never used the f/4 verison of 70-200 as I have the f/2.8 L IS II version ... between my 24-105 and 70-200 I prefer the 24-105 any day ... I do a lot of rig move videos in the desert and I find the 24-105 to be perfect both for its focal length as well its image stabilization. But if you are doing lots of video indoors (especailly for interviewing people close-up) than the 70-200 is AWESOME.
I'm not a videographer but I have all three lenses. If I could only have one lens it would be the 24-105. If you already have a crop camera, the 24-105 on full frame + 70-200 on crop makes a terrific pairing, which I use.