Rugs, Carpets and Carpeting - carpet squares instalation over tile and wood floor

my wife has been watching HGTV about these carpet squares or carpet tiles, I spent about an hour tonight looking up info on them all over the web, we took down a wall between 2 rooms and half was 12 in tile with about 1/2 in grount lines, the other was lam wood floors, where the wall was there is now about 5 in of gap wide and 1/2 in deep to the concrete, can I use quickcreet leveler, and can I install these carpet tile square things over the existing tile , what suggestions please, where is best place to get a deal on these, I see a lot of companies on the web offer, but I will be doing just under 400 sq ft so is it better to purchase locallty or internet and pay the shipping, my main question is the instalation over the floor adn the tile thou..thanks ..Mark

p.s. for the adhesion ....I saw where there was peal tab and stick and some knid of glue which meathod would work best over the wood floor of half the room and the ceramic tile with the big grout lines on the other half of the room

we just decided on carpet since no one in the industry knows anything about these, only trying to make a sale, I thought someone here might have an answer.....since some of you are in the biz