What's the most flexible form mailer for WordPress?

Hi there,

I am using cforms right now but it looks like I maxed it out.
I was reading about Gravity Forms but it also doesn’t allow me to do what I had in mind.

What I am looking for:
– multi-page forms (ok cforms does that)
– conditional forms [click one field and others appear on that page] (gravity forms can do that)
– maybe a checkout page that shows you what you entered before you actually send it (think amazon.com)

any ideas? i don’t care if it’s complicated. but so far I don’t know any more flexible alternatives.
A combination of cforms and gravity forms would be nice I guess.
Sure I could code it myself but then I think it would miss major security precautions etc.

Thanks!