If you feel like rewriting in Rails, make sure you consider the deployment factor.

In my experience, the only way to have a Rails app that is responsive and reliable without spending most of your time on deployment as opposed to on development, is having someone like EngineYard host it. But that costs 100s of dollars per month, which might be ok in your case, I don't know.

Maybe you want to go with Symphony instead.

I'm not so much against big rewrites, you just have to figure it out yourself if you think it makes sense.