It's a complete redesign of the core. It's nothing like an E8600 times two. That was actually the whole point of the Nehalem architecture (i7/Xeon 5500) - it was the first brand new design since the Core 2 series came out.
On the other hand, the Q9650 is very much like the E8400 times two. In fact, it really is just 2 E8400 dies put together.