If you're doing this purely on xml package, you can have the submit logic do a redirect to the current page using javascript and specify the filter parameters as querystring.
Then, on your xml package, you can expect the filter parameters from the querystring by specifying the paramtype as "request". Pass it over your stored procedures so you can filter the product display accordingly.
Sample Url
domainname.com?make=xxx&model=yyy
XmlPackage
HTML Code:
<query name="Products" rowElementName="Product">
<sql>
<![CDATA[
exec dbo.GetProductsFiltered(@make, @model, ... other params .... )
]]>
</sql>
<queryparam paramname="@make" paramtype="request" requestparamname="make" sqlDataType="nvarchar" defvalue="" validationpattern="" />
<queryparam paramname="@model" paramtype="request" requestparamname="model" sqlDataType="nvarchar" defvalue="" validationpattern="" />
... other required parameters .....
</query>