Get the S1. Given that you've been seriously thinking about it, you probably know that you won't profit much, if at all, and maybe at a loss too, but you don't really mind all that and you want to tinker with the hardware, the feel of generating 'money', watching your bitcoins slowly accumulate gives you a sense of slow and steady satisfaction, the S1 is currently the only one to get, both for your budget cap and its value proposition.
No, I dont expect to profit. I have done countless hours of research. I just want to be able to say "yeah, I mine Bitcoin."