The Birthday Massacre in my opinion deliver a deeper tone in their synthpop. They make you imagine things, and even relive moments of your past, all within the music and soft vocals. If anyone is interested that have NOT heard of this band, PM me & I'll get you in the right direction. Not don't let this comment say I dislike AiV. I wouldn't have uploaded it if I didn't. But I would say TBM is my favorite band.
I second Iggy Valentine's recommendation. The Birthday Massacre is a great band. They don't necessarily sound like AIV (for the most part), but I can understand why AIV fans would also like TBM.