Survey Monkey has integrations for both Marketo and SFDC, IIRC the Marketo Integration was quoted to me around $5k and the SFDC integration was quoted at around $20k for unlimited surveys and that includes both SFDC and Marketo integrations so you can pass information to either (or both) sides.
This post is a little old, but maybe you're still in need of a survey tool which integrates with Marketo. I suggest you to check out Marketo's LaunchPoint partners.
I invite to you to check out Survicate which integrates both with Marketo and with SFDC but there are many others.
Survicate specializes in micro surveys which you can place directly on your website or send them via Marketo's emails.