Live results with the ability to narrow search?

[jgarvin]

Reading this issue: https://github.com/syohex/emacs-helm-ag/issues/187 it looks like it is much easier to narrow results if you use helm-ag instead of helm-do-ag. However you only get real-time results as you type the initial pattern if you use the latter (helm-ag only starts displaying results after the first time you hit enter). Is there some configuration that will get me the best of both worlds?