The speakers are the older Nautilus 804s. But the stands will also work with the 804S speakers. The stands are from Sound Anchors in Florida. I have the taller floor stands up front and the standard height stands for the rears. They only sell the standard height stands now as a standard stock item. But you can ask them to custom make any height stand you want. These things are solid and have a lot of weight behind them.
As far as improvements to sound quality, I can't really comment. I bought my first pair of N804s used which had the tall Sound Anchor stands included with them. I've used them that way ever since I got them. I added the rear Sound Anchor stands more for increased stability than for any real sound improvements after a couple of....ahem....accidents with people visiting. With the stands, the speakers are definitely more stable and tipping them is a bit tougher.