The 7D is without a doubt a better camera as it is more weather resistant which makes a difference when you spend a lot of time outside and it is also much more rugged which ups its survivability when you bump it or drop it which you will do if you spend any time in the wilds. It of course it also an upgrade when it comes to the cameras specs.
For wildlife you will need good lenses of course. Im a conon guy so everything I have is canon but there are ppl here who use off brand lenses like the ones you mentioned and they have success with them. If you were to go canon and you had to pic one lens I would suggest the 100-400. it costs a bit but it still is a great lens even though it is getting up there in years. It even does a good job at things like butterflies and smaller objects so it will work for some macro stuff. After that I would get something to cover your range from say 24 to 100 and then I would get a macro lens specifically for macro work. lastly just to have it.. some kind of wide angle for landscape shots.
For wildlife though your first and primary lens needs to be something with at least a reach of 300 in my opinion and I think you will still find that to be short sometimes... I find the 400 to be short quite often and would prefer a 600 if it wasnt for the wieght of carrying it. with a body like te 7D though with its pixel count there is room for some cropping while still retaining image quality.
Lastly it really depends a lot on where you live as well as depending on the area you may be able to approach wildlife a lot easier than someone living in an area with a lot of red necks
Im being serious here :p Zack posts a lot of pics here and he lives in florida where the wildlife is used to human contact and you can get relatively close to it. He has told stories of getting within a few meters of a heron and having to shoosh it aways to get by it whereas that same heron species where I live will not be approachable closer than say 40 meters at best. With that in mind spomeone living in florida could probably do most of their work with a 300 or even a 200 whereas up here I would say 400 is the minimum.
I dont know much about your camera as the first one I got was the 50D and then I went straight to the 7D so I cant say how good the one you have is... I know if you get yourself a good lens in the 300 to 400 range however you will see massive improvement even with it on the body you have now. A lot also depends on your budget. I have no idea what the 100-400 is worth now but when I bought it it was $1800.00
hopefully someone whith the offbrands will comment on thier quality. I know KPR uses sigma and he gets good results.
if you go to my site below those are the types of results you can expect with a 7D and the 100-400 lens as the vast magority of pics on that site where taken with that setup.
Canon 7D + 50D + EF 100-400mm f/4.5-5.6L IS USM + EF 24-105mm f/4L IS USM + EF 100mm f/2.8L Macro IS USM
Pelican // Black Rapid // Think Tank // Manfrotto // Garmin
Reflections On Canadian Wildlife