There's an old thread of mine here
that talks about my experience with, colloquially, a "mirror lens" of the same construction and quality as the Opteka. Most of the image links are still working, too. The tl;dr version is that any decent-quality 200mm zoom can get roughly the same level of focus and detail after cropping to equivalent size.
The 55-250 that JAE pointed you to, would be a much better option. Since it's an EF-S lens, it's also smaller and lighter than a lot of the used higher-end zooms that you can pick up on Craigslist or eBay.