The Pentium D line are two prescot cores on a single chip, with no hyperthreading support.
So yes while it is a dual core processor, I don't think its really in the same league as the Core 2 Duo line.
And whether people want to believe it or not. The Saturn was an incredibly complex machine, and the fact it had multiple CPU's makes ALL the difference in how it is emulated, as well as the power required to emulate it.
You can't compare it to emulating a PSX either, because simply put, the Saturn was the more powerful machine of the two.. It had more processors and more RAM. By default it was the more capable machine, and if Sega had not screwed up all its marketing attempts, would have been a great life long contender against the PSX.
Also you need to realize that game consoles up to this point in time, were using highly customized RISC CPU's which are completely different from x86 CPU architecture. RISC CPU's are highly efficient at mathematical calculations and a lot of the stuff involved in rendering graphics, and it takes a great deal of extra power to match the capabilities of a RISC CPU when you are emulating the chip on an x86 platform.
Programming skill always comes into play, as we can see from past emulators that have gotten better over time, but the Saturn out of all consoles emulated, has historically been one of THE most, if not the single most, difficult to do. That is why there have been so few Saturn projects and the ones that exist now are moving so slowly. No one had either the skill or the balls to attempt it on a regular basis.
And yeah I wish Steve were hurry his butt up and get that Saturn emulation integrated into Fusion.. My mouth has been watering ever since he e-mail me that full-speed w/sound youtube video of Burning Rangers.