I've never heard of the "Cardas" method (and am highly skeptical), but since you brought it up you've apparently found it lacking. Why not just start out with what PAP suggests and do incremental adjustments to zero in on the best results for you ears and music preferences? Or start out with the equilateral triangle and change one variable at a time (like the distance from the front wall, toe-in and separation, etc). You'll never find a cheaper, easier way to improve the sound of your system. It will take a little while and effort because of the interactions with the boundaries, but that's also what will give you some great enjoyment and commitment to your subjective opinions you come to as a result. Hopefully you have a listening space big enough to do meaningful, i.e. clearly audible changes - that you can live with - and have a supply of damping materials, aka rugs and so forth to get control of reflected sound. Good luck and have a lot of fun - maybe you can share your process and describe the results when you are truly happy too; I'm sure there will be many folks here interested in what you discover.
