Do you really want to see what happens when you go from a 20 or 22 megapixel sensor to a 46 megapixel sensor? Do you want to see how the lens affects sensor sharpness? Take your lens, mount it on your FF camera, take a photo that shows off sharpness. Then take that lens, mount it on a Rebel, and do the same. You will find that only lenses of superior sharpness will give you a sharp image on your Rebel...... and that is what will happen when you go full frame high megapixel....
Unless you have a camera bag full of the finest L-glass, you can rant on and on about which sensor and which camera outresolves who..... but out in the real world most people have bought into a SYSTEM.... and by far the most important part and the most expensive part of that system is the glass....
You can take the crappiest Nikon DSLR, put a high end lens on it, and it will outresolve the finest Canon camera with a kit lens. Likewise, take the crappiest Canon, put on some high end L-glass, and it will outresolve the finest Nikon with a kit lens.
You want to know the order of things?
#1 - photographer
#2 - glass
#3 - camera
..... and the glass is an investment while the camera can be best thought of as expendable.
Sorry for the rant, but this thread has degenerated into another DXO/SENSOR/NIKON/CANON arguefest, most of which has nothing to do with the topic at hand..