Conditional Category Post Dropdown

Hi Everyone,

I have been searching for a plugin like ajax-category-posts-dropdown which is compatible with the latest version of wordpress. Ajax Category Posts Dropdown

A) whether I can present 2 dropdowns for user, the first -> to select category from the first dropdown and then present a second dropdown to select a post from the chosen category. I have seen it in oscommerce http://projectorlampgenie.com but I want to use this in wordpress and I could not find such a plugin in wordpress (ajax category post dropdown is outdated and doesn’t seem to work with ver 4.0).

B)I want to go a step further, the above website is an exclusive website for projector lamps therefore they have only 2 dropdowns, whereas, I want to extend it to three dropdowns like this:- First Dropdown Select Product (Category) –> Second Dropdown Select Brand (sub-category) –> Third Dropdown Select Model (post title)

I am not in favour of using woocommerce or any other shop script as they are burning in server resources on host for huge queries.I am talking about more than 20,000 products.Therefore I have decided to stick with categories and posts.

Please let me know if anyone has worked upon this.

Thanks in advance.