Hi Ville!
If you're looking for something that you can do outside of the checkout flow by a followup email, I'd suggest Fluid Surveys as a great option. On the site, I've seen it called 'adaptive quizzing' where you use results to pre-set recommendations. Sites like Ipsy use them to decide what goes into their monthly subscriptions.
It can be custom-coded in. I know that eCommerce Fuel has done really similar things for customers before, like in this article: http://www.ecommercefuel.com/shopify-vs-magento/
I'd recommend talking to a Shopify Expert to see if they could help include that on a site. :)