Firstly remember you have orientated your house's windows well so you probably have more leeway & can chose something you really like the look of even though it may not rate as high as some other options.
I agree with J-A that heavy curtains with heavy block out linings fitted with a pelmet are the best at insulating windows & the heavier the material the better. But this is a much more formal look & may not be what you are looking for through out your house but would suit your front living areas if you want them to be more formal & these are the windows that probably need the most sun protection.
I'm a big fan of roller blinds as they are sleek & simple & if you want to add shears they retain a modern look. Verosol is a brand used in high rise office buildings which need to meet energy guidelines, the most efficient have a silver backing to reflect heat.
Another option I've been looking at are honecomb blinds as the air pockets create an insulating barrier. I sent away for some samples of this brand
http://www.blindsonline.com.au/honey...l-light-filter and will be looking into these further. The small pleat looks nice and aren't like the larger pleats you see in offices, you can open them from the top as well as the bottom so quite versatile. I started looking at these as an option for keeping a room warm in winter as well as keeping heat out in summer. There are other blind places that sell them, google 'double cell honecomb blinds'.