100% You need a solid state, it will change the whole experience. Use it for Windows and the apps, store anything like pictures/videos etc on a mechanical HDD where you have the space.
The Samsung 840 Pro's have very good reviews, a new version of it is due soon which is meant to be quicker. Windows 7 will consume a good 20gb and you don't always get the full capacity so I'd say anything over 128GB will do for that along with a larger storage disc.
Most of the intels now come with integrated graphics (I3/I5/I7) which isn't actually too bad performance wise, could knock off a significant figure if you go down that route. USB3.0 is backward compatible, so if you can get it, go for it. SATA3 too if you can, an SSD will saturate SATA2 (Although you wouldn't probably see the different)
RAM wise, around 8GB of good brand DDR3 - Corsair or the like.