It might be worth adding some YN460-II flashes onto your shopping list to pick up at some point if your 430EX isn't quite powerful enough, and then just double up on flashes and trigger them via RF-602 receivers.
I've got two of the YN460-II flashes at the moment, and I let a friend borrow them during an outdoor shoot a couple of Saturday's ago as he only had high voltage Vivitars with him, and they obviously wouldn't work with the RF-602 receivers. He loved 'em, he's got a few of those on his shopping list now.
I'll definitely be picking up some more at some point.