I've owned and operated an e-commerce site for 10 years. The original/current site is written in .asp. It's been a functional site for us, but we have a sense that it's time to rebuild. Just like the an old car needs to be replaced every so often, we're at a point where we're looking to replace our web site with a newer version. Our goals are to increased SEO functionality and improve site navigation.
Most of the SEO folks that I've spoken with want to completely re-do our web site. Perhaps that's necessary, but it might just be up-sell. My challenge is to determine what I would gain by dumping the old site and starting fresh.
I'd appreciate some feedback on this question; if you could build a new website today with all the SEO bells and whistles you could ever wish for, how would it be written? .asp, PHP, html5, something else?