Hi,
It just not a good idea to install CleanMart on top of an another VM-Ready Template. It would be hell of a work, even for me. Because you have to eliminate the Virtuemart influence from the existing Joomla Template first, then install CleanMart.. so much work!! wouldn't worth it.
It is just much better idea to first get the Joomla Template that you like the most or pick the the most appropriate design that will get along with the eStore you are working on (pay attention to; menu navigation, slideshow component, responsiveness, module position variations, blog support, footer/header designs, light-weight, technologies, CSS3, HTML5 etc..), It won't be hard because there are millions of Plain Joomla Templates available on the web (T3, gantry, yootheme, gavick, rockettheme, joomlart etc..). Then install the CleanMart on top of it and BOOM! you get the coolest, up-to-date VM-Ready Joomla template ever ;) and its design will be unique to you.
But of course, SportMart is also cool too ;)
Regards