This is a pretty nice spreadsheet that you can use to enter two setups to compare some ratios. It obviously won't tell you how fit you are to turn the gears, but it gives a nice overview of cog to cog percentage jumps and speed based on gear and rpm. Just have to edit it with your inner/outer ring sizes (in red), edit the cog teeth column, and then edit the rpm to see how fast you'd be going. It assumes a 700c road tire.
10sp_cassette_jump_chart.xls.zip