Just GA. Now that you mention it though, given all the pop-up blocking, my numbers are likely underestimated. I'll cross-reference with server logs next time.

re 6 vs. 150 subscribers. The trick to getting people to sign up is... (you are not going to like this)... a pop-up.

People on forums will complain about it.

People will sign up with fake and insulting email addresses to spite you. You may even get upset.

But my god will you gather emails from the people out there who actually care about the work you are doing.