It won't fit all after market but my brother got an evo 212 92mm with 3 contact points. The 7870 is an open box item so you might not get all accessories that it is supposed to come with, but I almost bought that card myself. I can understand why you would get the more expensive one, but the asrock will save a lot of money. I wouldn't switch mobos honestly. There is a chance that you will have to format your hard drive. Also you need consider if you could spare an extra $100 right now, because if you are going to get another cpu in a few months then, you will be out possibly $100 for no reason, but if you absolutely can't then you could do that. The i3 2120 is a great gaming cpu, it just can't do a lot of tasks at once. Also the ivy bridge stock fans are pretty good.
What I was saying, is at if you get a new mobo with the i5 you will need to format. I didn't notice the bonus key, it is worth it then. Well the only thing you really need with a card is the card itself. Everything else that it comes with just makes it a little easier, IE the install disc, you can just get the drivers from amd's website though.