Well here is some facts
1) there are "Performance test results" for each product at http://routerboard.com/
2) low end RB7xx or RB9xx are very inexpensive.
So buy one of those, test its maximal performance and then use proportion that you can get from comparing tables of both products.
From those tables you can also see what is configuration impact on performance - it severity also is important.
i know it sounds like witchcraft
but it works, and works best with similar products, like having CCR1016 you can calculate what CCR1036 will be capable to do.
but this approach have one big plus - configuration is exactly the same as you will have on new board, so that is constant.
With great knowledge comes great responsibility, because of ability to recognize id... incompetent people much faster.