If you're not interested in buying Koins then how about an Upgrade? To be honest it depends on how desperate you are to change your Username, because if it doesn't bother you that much just build up your account with HQ Posts and Threads etc. and you'll be at 2 Koins within no time at all! If it does bother you I recommend purchasing the Onyx upgrade as another user previously said, it's the cheapest one of the 3 and you don't have to purchase the additional 'Donator' award required with the more expensive upgrade "Power". Buying Onyx also allows the user to change their username whenever they want completely free of charge.