Yota, the benafits of a light weight flywheel are huge. I know that you are planning on getting a LSD, you should definately get a flywheel too.
Having a light flywheel offeres a reduction in weight where it really counts, which is rotational mass. This means bigger gains will show up on a dyno because a lot more horse power will actually reach the wheels. This is due to it taking less effort for your engine to turn the flywheel, and is the same result that peeps go for by adding light weight wheels to their cars.
Your car will feel much much more responsive with the light weight flywheel too. When you give the car a little gas, it really goes. I noticed a huge increase in acceleration after I had mine installed. Not only does the car accelerate much faster, it also slows down much faster, especially when you downshift, which I love.
You might want to look into the Blitz active clutch, yota. I have the Toms flywheel with the TRD clutch and LSD, and I love them, but I wish that I had the option of getting the Blitz because I would have seriously considered it. The Blitz active clutch comes with a light weight flywheel, and I have heard that the flywheel is even lighter than the Toms. I'm not saying that the package is better than the Toms/TRD setup for sure, but it is definately worth looking into, Blitz products are really good.