The higher end SKUs often boast better overclocking. Ones I can think of off the top of my head are MSI Gaming X and ASUS ROG Strix. At the same time, the lower end cards are fine for a mild overclock, but it ultimately depends on what you mean by "I want to overclock" - if you're going for big overclocks, go with a more expensive GPU, as they often have better coolers. If you're fine with a mild one, something cheap like an EVGA Superclocked will do fine.