why don't I take pictures inside ? Is it because of my current limited functionality with my kit lens ? What I'm wondering if going further to a 16-35mm and 24-70mm combo would change my style, have others made the leap and found a new interest in lower light photography ?
I am shooting indoor / low light (with environmental light) with a 40D and Canon 85 mm / F 1.8. I have to say that most photos are, from a technical point of view, horrible, but it gets the moments.
It's an unsatisfactory / limiting experience. I am shooting ISO 3200, shutter priority at 200, and getting whatever F-number. At sub F2.8, although the quality is good in good light (for indoors, that is), it's unsatisfactory in most indoor environments, but even when the quality is good, the DOF is frustratingly thin.
To understand what quality you can get, take photos with your current gear and look at the histogram for the photos which the camera says are correctly exposed; it doesn't matter if you get a 1 second exposure and blurry images. If it's hefty throughout the first two thirds of the brightness range, there is enough light to get good quality with good noise reduction (think LR 3 good).
You normally get a hefty histogram if you shoot in broad daylight, near a window, with good indoor light (for instance, the usual lighting conditions in a small room with bright / highly reflective walls).
If the histogram shows pixels crowded mostly in the first third, the quality will be bad. The reason is that you have little tonal range in that area of brightness, so tones will be mudded, especially if you brighten the images (you would want to do this because although the camera says that the photos are properly exposed, they are dark when viewed afterwards).
So, your 450D will not get you good quality indoors even with an F2.8, but maybe you can shoot in the good lighting conditions that I was describing (note that even in those conditions, I still usually get an F-number lower than 2.8 ). What you need is a camera which can do photography at ISO 12800. For this, I would say that either 5D2 or the future 5D3, combined with an F 2.8 zoom lens, are necessary. Since money is not an issue for you, I think this is the best practical combination.
If you like to shoot full sized people, rather than portraits as I like, you could also try a sub 50 mm lens with an F 1.4 or so. The DOF would not be an issue in this case.