What Occupies My Brain

I have been agonizing about upgrading to a Canon 5D mark ii. This means I pass hours typing "Canon 5D vs 40D / 5D comparison with 4D / 5D low light portraits / 5D review" and such keywords into Google, and then pore over all the results, read expert and lay person reviews, look at photo examples, and I forget to eat.

I am also trying to figure out - have I maxed out the photo quality on my 40D? Have I done everything I can do - both on camera and in the process of editing - to make the best possible picture? I can't answer that with a confident Yes, because Photoshop offers endless capabilities I could never hope to fully master.

The main attraction is the 5D's low light shooting power. I use natural light as much as I can, and if there's not enough light, resolution on the 40D can get speckly.
The deterrent is of course, cost. But then I remind myself - this is not some expensive hobby. I'm doing this professionally. I am constantly aiming to take the best pics possible for my clients and myself.

Cameras are returnable. I could buy, try, and return if dissatisfied, though all reviews assure me that once I get my hands on a 5D, there's no going back.