Sorry, I'm an idiot!
Well, I'm obviously not a battery guru. But, I also miraculously ignored the fact that the lithium Ipower battery that you all were referring to was, in fact, actually rechargeable! This whole time I thought the lithium 9v you were referring to wasn't rechargeable... :/
So, now I look like a fool... and therefore this thread should be deleted at once!!!
Seriously though, I'm sorry about that. And really, thanks for the help and information guys. The choice is actually as clear as day now. Thanks.