There's about a 2:1 ratio between handlebar effect and stem effect; when measuring from bar to stem. When measuring conventionally, it's about 1:1.

Still, I'd recommend trying the 70 first before you do anything else. It's a quick, painless swap; you might find that you like it better that way, who knows. If you don't, you can try a handlebar swap, but I think you're going to end up needing a new frame.