Intel IGPs are crap when it comes to gaming, dont even try. Just get a cheap card like an HD 4650 from ATI, it will perform worlds better than any intel IGP.
Get a HD 3300, I'm at 40-60fps on low-med settings everywhere except dalaran and the odd instance.
Depends.
If the OP already has an Intel platform with motherboard and CPU it would be foolhardy to upgrade both motherboard and CPU for an incremental boost in fps.
A discrete card would be better in that case.
Hoever, if the OP hasn't built the system yet, the HD 3300 would make reasonable sense.
Actually if you look here http://www.tomshardware.com/reviews/best-graphics-card,2404-7.html
you can see that the X1250(the IGP from the 690 chipset) is actually two tiers above the GMA X4500, the only difference between the X4500 and the X4500HD is a bit of hardware acceleration for media formats.