Yeah you definitely don't need to be shooting on the standard picture profile. Also if you are shooting at 30 fps you need to use a shutter speed of 60 (1/60th) and if you are shooting 24fps use a shutter speed of 50 (1/50th). Try sticking to ISO's in multiples of 160 (160, 320, 640, 1250) but I wouldn't go over 800 for professional work on the 7D.
I have a feeling that the f/4 of the 17-40 may be holding you back. Since the shutter speed stays fixed, your next method of letting in more light is lowering the aperture, but f/4 is the limit. So if your shutter is at 1/50 and your aperture is at f/4 and you're image is still underexposed, then your only option is to increase the ISO. But the higher you increase the ISO, the more noise is introduced. This leads to all kinds of bad image quality, but a little added lighting can help tremendously in keeping your ISO as low as possible.
Also, don't use the standard picture style. Use Neutral, turn the sharpness absolutely all the way down (to the far left) and cut the contrast and saturation down a couple of clicks (maybe -2 from center). Turning the sharpness down is crucial. Standard picture style tends to crush the blacks so you end up losing tons of shadow detail. I like cinestyle for some situations, but if you're shooting with limited light it can end up introducing quite a bit of noise. And there are some situations that you may not have time to do much color correction and with Cinestyle you HAVE to grade it. I know the Also make sure you have auto lighting optimizer, highlight tone priority, and noise reduction stuff turned OFF. Use Kelvin manual white balance.
If it's "not the quality you're used to seeing online," it's because a lot of the videos you saw were shot with very expensive primes, which let in more light (which allow you to shoot at lower ISO, which leads to less noise/better picture) and are much sharper than zooms. Also, stabilization is a big thing, DSLRs just don't have the ergonomics to operate handheld and still get good results. You need at least a tripod with a fluid head or some type of shoulder rig, and a follow focus with an external monitor or evf to get the type of results you are looking for.
If the footage doesn't look good off the card then it's not a post-processing issue. I rarely do much in post to affect the image quality, and generally when I do color correction it's just minor tweaks to the white balance and levels. iMovie is a pretty basic editor, if you use that now I would suggest upgrading to Final Cut Pro X if you do upgrade. It will be much easier for you to learn than Premiere or Avid. I've been using Final Cut Studio for almost 10 years, but I've used Avid and Premiere and think they are both equally capable, FCP was always my preference. I hated FCPX at first but now that I've gotten used to it, it's absolutely insane how fast I can cut projects. I went from cutting 2-4 music videos/day to 10-15. But the thing is, your footage should look pretty good coming off the camera regardless of what editor you end up putting the footage in. Unless your export settings were totally out of whack then I would focus more on your in camera settings.
These cameras are not the type of video cameras that you just point and get movie-like results, I've spent thousands and thousands on accessories to make my cameras function more like video cameras. It's definitely not an "automatic" camera, you have to pick your settings carefully and not let the camera decide too much for you. You just have to remember that these cameras are always still cameras first and video cameras second, it takes a lot of trial/error and studying to get the type of results you're looking for.