Well, I would suggest the Jawbone2 even though it is pricey --- 129.99. But, despite the price it is probably the best bluetooth headset out there and my friends loves the first Jawbone.
The S9 is way to go for workout and BT. I have those and the Jabra BT adapt and it works great with my Nano.
So the S9 doesn't hit the back of your neck? I'm not sure how it would fit well since it doesn't adjust.
Well it does "rest" against the neck, but I dont think I would want something firm against the back against the back of my head anyway.
EDIT: Actually, here's a better question: which is better, the S9 or the HT820?
These pictures alone should answer that question. The size of the HT's makes them crummy for any activity that is more then just walking. I will say they sound better, but they would not be good workout headphones.
I have seen the S9's in ATT stores that you could try on.