Single brake conversion advise

[scholeno18]

I'm looking to do a 21 in front wheel. I'm toying with doing the single brake. I understand that I need to upgrade the caliper to a 6 piston. Has anyone done this and kept the stock rotor and just used the 6 piston? If so what's your experience opposed to upgrading to the 13 in rotor? I'm having a hard time finding a decent price on a 13 in rotor. Any suggestions for what caliper and site would be appriciated as well.