So the 600D is probably the best choice for brickfilming as far as camera bodies go, and a good choice for amateur filmmakers, so it's a good choice, but I'm assuming you already knew that. As far as the kit lens goes, it will hold you, but I'd upgrade as soon as possible. For brickfilming, and any stop motion, I'm a fan of manual focus M42 screw mount lenses. I have a video here: https://www.youtube.com/watch?v=QMcfTzvq9do explaining why they're ideal for stop motion. Here's the last video I shot with the kit lens: https://www.youtube.com/watch?v=fXMXeqotBnM , the same lens was kitted with the 550D and the 600D, and here's a video with an old 50mm Pentax screw mount lens: https://www.youtube.com/watch?v=oM7_qHRP_gw. The Canon kit lens has a fair bit of flicker, while the Pentax gives none, and the image quality on the Pentax is way better, in my opinion. You can find these lenses online or at just about any camera store, and a lot of them go for less than $100 USD. You can get an adapter for EOS cameras for like 20 bucks. The screw mount lenses are great because the distance from the back of the lens to the sensor is almost the same as an EOS lens, so they can focus to infinity, which is a problem with adapting a lot of other mounts to EOS cameras; although not focusing to infinity probably wouldn't be to much of a problem with brickfilming specifically. As far as for live action video goes, the kit lens isn't that great either; it'll sort of hold up, until you use something else. If live action is something your really into, I'd look to upgrade as soon as possible, but if your just dabbling, it's probably fine, especially since YouTube compresses away a ton of quality anyway. As far as still photography goes, take it from a semi-professional photographer, it's a bit crap; powerful is probably the last word I would use to describe it. That's kind of a lot of information, so if you have any questions, just ask, I love this stuff. 
