Hi Scott,
All Multibridge models are designed to act as standalone convertor and you can also connect a Multibridge to your PC via a Decklink card such as the DeckLink HD. This provides the HD-SDI connection to Aspect HD, regardless of whether you are using the component connections of the Multibridge or not. Multibridge seamlessly converts between HD analog and HD-SDI and vice versa. So as far as Aspect HD is concerned, it is just working with HD-SDI.
The new Multibridges with PCIe include a PCIe adapter card for your PC. As far as your PC is concerned, it will think that it is just working with a DeckLink card via HD-SDI and that fact that the Multibridge unit is external is of no consequence. In other words, Aspect HD should view the Multibridge with PCIe as if it were just any DeckLink card with HD-SDI.
So yes, you should be able to use component HD analog and have Multibridge convert it to HD-SDI for use with Aspect HD as it will be just like using a DeckLink HD card.
Regards,
Luke Maslen
Blackmagic Design