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That's a lot of gear to carry in a small cheap bag. The Sigma 150-500 and 16" laptop are going to be issues. I don't know what you would do with the Sigma 150-500 in Vegas. You might want to reevaluate what you want and try to be realistic. Do you want small or do you want to carry everything? I own four bags of various sizes. I think my GF had that Tamrac bag. It was nice, but too small for everything you want to carry.
I used to own a TT Streetwalker HD. It is a nice bag and will carry a lot, but I wanted to carry a bit of non-photo gear at times, such as a jacket and food while hiking. I ended up with a Lowepro Pro Trekker 400 AW which has about the same internal camera space as the Streetwalker but also has several large external pockets. What I really like about Lowepro is that the laptop compartment can be used for other things when it isn't needed for the lappy. And I like the straps and weather proofing better. The Trekker 400 AW is a big bag and will swallow up everything you need to carry. I routinely carry a 300mm f/2.8 in mine. I just returned from 3 weeks in the UK with this bag. It carried two bodies, 70-200 f/2.8 and several smaller lenses. My 15-inch Macbook fit with no room to spare.
Coincidentally, I bumped into another photographer on a trail on the Isle of Skye. He was using a f-stop Tilopa BC and we talked a bit. I had tried the Tilopa, didn't like it, and was very happy with the 400 AW. He had tried the 400 AW, didn't like it, and ended up with a Tilopa. So there you go. Different strokes for different folks. We did agree that Canon was better however!