Hehe, I like hanging out with both guys and girls! I'm pretty much a guy in a lot of respects...and since I'm bi, I can check out girls with the guys and guys with the girls! Booyaka! xD
Erm...>_> Anyway!
Awww, you're so pretty! Cute guys, too, and man, Eric looks like one of my best friend's fiance! But hrm...tough situation. Things always get complicated when it comes to friendships that get like that, but I say if you guys are best friends and really trust each other, you could do it without harming your friendship. And in my own humble opinion, the best sort of relationship starts with friendship and builds naturally, and a lot of people say that their partner is their best friend. Well...you kinda already got the best friend thing covered...^_~
I'd just talk about it a lot in advance. Explain your feelings and concerns, get it all out in the open, and then if you guys want to--give a relationship a try. You might find it awkward and uncomfortable...or you might find that it feels really natural and doesn't actually feel much different than the friendship does, except with a few added bonuses. Take it slow and, of course, communicate! That's the most important part.
And I guess another thing I've noticed and learned from experience...well...a lot of people get hung up on the whole "relationship" label, and it's that label that makes everything...weird. I guess what I mean is just remember that, at the core of everything, this guy is STILL your best friend. ^_^
And of course, if it doesn't work out and in the end you guys feel more comfortable with what you had before, well...you can still go on being best friends. It really can be done, especially if you guys have that strong friendship to begin with and make sure to communicate.
So, yeah, in a nutshell...if you guys both feel the same way...it can't hurt to give it a shot and see what happens.