I'm planning to build a six-legged, 18-servo walker robot. I'll start by perfecting a single leg and continue on from there. I'll be using a board from my first project, Parallax's Boe-Bot. Could anyone suggest a good, low-cost servo that I should use that's available in the USA. I'm hoping to use servos that cost less than $5 each in order to keep the total cost down.