I would like to point out that Chromecast, while extremely cheap, is an odd little device. It requires a smart phone or tablet to work properly, so it's really a "middle man" situation.
The Ouya is over-priced at this point. If you want a "hardcore" gaming device I think the new (Amazon) Fire do-dad is more bang for your buck and there are even more powerful devices on the horizon competitively priced, some even using the Ouya interface (if that is a plus for you).
But if you need it right this instant, the mk series, as ark suggested, is probably the best route.