I wouldn't got the route of self tinting. That usually doesn't look as good, work as well, or last as long. Most local glass/window shops will have a list of reputable home and commercial tint companies in your area. We sell a decent amount of tinted windows to customers in your situation. However, if they aren't looking o replace the glass we refer them to a tinting shop.
Depending on how old your current windows are and how much you want to spend you have a few options. Tinting is the cheapest, next cheapest is buying new insulated units that are tinted, the third and most expensive (although there is a tax credit - 30% up to 1500 for qualifying windows) is all new windows (glass and frames).
One warning...the tint can raise the temperature of the air between the panes, which could cause them to prematurely fail and when the weather changes you will be left with condensation/fogging going on.