why change the psu to a modular one. they aren't that much easier to work with tbh. i have the 650W you initially chose and my cable management is far better than when I had a modular psu. don't see why you should pay more for a less powerful psu, when the cheaper more powerful one is easy to work with.
and i'd get the 4870.
I agree I didn't get a modular one because I use a lot of drives.
At the moment I only got the extra PCI Express connector that I don't use the rest of them I use.
I saved myself a score and used that money somewhere else.

I got the 605 W Cosair TX. I would reccomend it.