Hi,
I think the foam is a good way to go, but on the pricey side.
There are several types of foam, so I'd look into that -- both R value per inch and permeability to air flow are different between foams.

If you want a good and cheaper solution, then I'd say carefully seal all the openings between the living space and attic -- everywhere a wire or pipe penetrates, vent pipes, chimneys, ducts, light fixtures, can lights, ... Seal them all to prevent air from exfiltrating from living space to attic. According to one study, living space to attic airflow is larger than infiltration around windows, doors etc. Then blow cellulose in yourself -- the big box hardwares will loan you a blower. This is cheap, fairly easy, and is very good insulation.

Make sure you also seal any heating/cooling ducts at every joint with duct mastic.

the book "Insulate and Weatherize" by Harley is very good.

Gary

If you are going to spend the money to do the upgrade - be sure you have each estimator tell you how high the R-value will be when completed. We also asked ours to include spraying into electrical outlets where I hear drafts run rampant.

If you are going to do it, this is a good time because of the 30% tax credit... Makes the pain a little easier to bear.