I added about 12-18" inches more of blown in to my house. Did it myself. If you buy 10 bags of the Attic Cat blow in insulation at Home Depot you get the rental of the blow in machine for free. Very simple job to do if you have any kind of do-it-yourself skills.
Had the attic roof sprayed with foam. Even in summer days, attic is warmer than the house but not oppresively hot. More expensive upfront, but should pay off on lower energy bills.
My dad did the foam on his house.....I love it and wish my house had it, but it was expensive and will take a long time for payback. Blowing in your own from Home Depot or Lowes is easy and relatively inexpensive (and a good budget option).