That Frozen Concoction

There's only one place nearby that has frozen cocktails, and they're kind of pricey. So I decided to get the necessary equipment to make them for myself. I got a blender at Target - making sure to get one that crushes ice well, and this one did so quite satisfactorily when I tested it - and some margarita mix. Now I need tequila, but I wouldn't know a good tequila if it jumped up and bit me.

So, a question to those more versed in liquor lore than I: what's a good tequila? And a rum would be nice too, as someday I intend to make daquiris.