Is your budget limited because you are a student or still living with your parents, or because you are just poor? (Don't answer that here; it's a question for you to answer for yourself.) Basically, do you expect to be poor forever, or do you expect to have more money to spend on toys in the future?
I own a Canon system (a 40D in fact). And right now, I think Canon has fallen badly behind. If someone were buying into a DSLR system today, I would recommend Nikon or even Sony mirrorless (their lenses are overpriced though). So you're moving backwards IMHO if you switch to a Canon 40D.
DSLR bodies are always being replaced by something better every few years. The lenses however are upgraded about every 20+ years. So if you're buying a DSLR, you're really should be looking at the lenses, not the body. If you're planning to use the 40D with your 50mm lens only, and in the future when you have more money you plan to switch back to Nikon, then I think it might be OK. But if you plan to add lenses to the 40D and are tempted to get Canon lenses, then I think you're making a mistake and would be better off sticking with Nikon (unless you are deliberately choosing to switch to Canon for the future).
Also, the 40D's low-light performance isn't great either. The only time I use 1600 ISO is when taking astro photos. For regular photos I won't go beyond 800 ISO, and I only use 800 if I have to or the photo is going to be reduced in size. 800 is noticeably worse than 400. I haven't used a Nikon D60 so I don't know if it's better, but I think you'll be disappointed if you're expecting a huge improvement.
https
/www.dpreview.com/reviews/canoneos40d/18