these days beginner DSLRs & current mirrorless cameras can get pretty decent images, but it will really depend on the user too. I would say 600D and your 1100D, you wouldn't feel a big difference between the two..

big body doesn't mean it's tougher..got pros and cons, big body may FEEL tougher, but it's more difficult to carry around than a mirrorless/compact..believe me I've been using DSLR system for more than 6 years..just dumped my entire system for mirrorless a few months ago.

I would recommend fuji x system as I'm using it now and I really love it . you can take a look at the XA-1 or X20..both around your budget I guess..

depends what lens you are looking for..1.3k-1.4k can find a fuji 35mm f1.4..canon's equivalent is about 4k I believe..of course it's not the same but it's a cheaper way to experience 1.4 with no compromise to IQ..build quality is good too