Hard to go wrong by upgrading your footbed. Get a good one, and you can transfer it to your new boots if and when you do decide to upgrade. But that should be the first step before you change or upgrade anything else. If you like the footbed, but still think you need to improve the fit of the boots, particularly in the heel cup, you can add pads that take up space in the boot. Any decent boot fitter will have these type of materials on hand. If you want to do it your self, you could go to Tognar's site and find all kinds of info and supplies for boot fitting. You wold be looking at the "Narrowing Pads".
http://www.tognar.com/boot_heater_warmer_fitting_dryer_canting_dryers_ski_snowboard.html
They range from 4.00 to 6.00 per pair, depending on which area is troublesome.
If that doesn't do it, and you still want to keep your current boots, then get a thermo flex liner from Bomber. They run 177.00. Take them to a bootfitter and have them bake them for you and will have your custom fitted boot. You could do it yourself, but it is a little difficult the first time. You can find the details on "home baking" here on Bomber if you are adventurous.
The thermo fit liners will also pack out over time (all liners do). When they start to get packed out again, just have them baked again. This can be done multiple times.
Not sure how much you would want to spend on an old pair of boots. These steps are certainly cheaper then a new pair.