What is the most cost effective way to retrofit insulation?

I have a home built in 1996, 3800sf with a pool that has utilities running almost $700 in the summer. I live in climate zone 3A. There are two a/c units with gas heat which are not efficient at all based on the yellow energy guide sticker. There are two gas water heaters. Both the a/c and water heaters are located in the attic. The tops of the ceiling joists are not covered by insulation and there is no radiant barrier. The second floor has some walls that border attic space (like a knee wall, but for the an 9ft wall). Several rooms also has cathedral ceilings.

The exterior is mainly brick with some clapboard siding. The house is oriented with the front facing west and has many large double pane aluminum windows (argon or krypton is doubtful).

As a side note, I plan on opening up some exterior walls to investigate termite damage, so I will be replacing drywall.

What are my best options to get these down to a more reasonable level without too much additional costs? I am reluctant to rely on energy modeling software because of how unreliable it can be so I am interested in personal experiences and not just the numbers. Where possible I will be doing the installation myself.

The ideas that I am throwing around are:

Adding blown in fiberglass to attice
Install radiant barrier
Insulate knee walls more
double stud the exterior walls with fiberglass or cellulose since the wall
foaming cathedral ceilings
foaming the attic rafters and sealing it completely
5kw+ grid tie solar panels
solar panels for pool pump alone
replace water heaters
replace a/c units
replace west and south facing windows or all windows.