Gee, I was going to recommend mine, but now I kind of want
yours. 
Anyhow, for a more budget-minded backpack, here's what I use.
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There's a compartment in the back that you can't see on the photo, although the zippers are visible on the left. It has a sleeve in it that's intended for a laptop. I keep my Boss ME50B (a large multi-effect) in the sleeve, and the rest of the compartment has a power strip and extension cord coiled up in it. So it's definitely roomy. The main zipper on top opens to a very large compartment in which I keep a ton of cables, two straps, a PCM recorder, a roll of duct tape, etc. The compartment that opens by the next zipper down has a sleeve inside it large enough to hold a small tool kit, and I keep other various tools and spare string sets in the rest of that compartment too. And so on and so forth. My point being that there's lots of room.
I think I bought it three years ago or so. I have it stuffed full with about 25 lbs of stuff. And after all that abuse, it's starting to show signs of wear, but it's still got plenty of life left too.