If you are looking to replace downlights (other than ones over the kitchen bench) you should replace them with batten fix or pendant lights, mounted below the plasterboard. This way you can insulate over the top as well as reduce electricity usage. I have just done this in my house. It also allows the CFLs to throw more light as they mounted within the room, so your overall lighting / lumens should be similar.
I paid $13 each for most fittings plus the globes.
Any pictures, links, catalogues ?