Just got my HT-S9100THX yesterday. I ordered it from electronicsforless.ca and it showed up rather quickly.
I'm still waiting for my HDMI cables from Monoprice, they should be here this week. Without the benefit of HDMI, my first impression of this system is very good. It's very loud, and crystal clear at all levels. I have no complaints.
I originally wanted to go more high-end. I started looking at the TX-SR806 or maybe the TX-SR876 receiver coupled with Axiom Epic Grand Master - 500 series. This would have cost about 4.5 times the money, and might very well have been worth it, but I couldn't resist the bang-for-the-buck of this system.
The only complaint I can come up with is the size of these speakers (while crystal clear and more than loud enough) don't offer the displacement that a larger speaker can offer. With the tunes cranked I don't find that "pound-in-your-chest" feeling that a larger speaker can offer. For literally a fraction of the price though, I will easily do without this.
I will be adding an HD FTA, and HTPC, and a Blu-ray to this setup in the upcoming weeks or months, and I will post any differences I find with the addition of HDMI cables as soon as they show up next week.