PCI vs. PCI-Express sound cards

[SlyReaper]

My motherboard only has 2 PCI-E slots. One is blocked off by my graphics card cooler, the other is very very close to my northbridge heatsink, so much so that I don't think a long card would fit in the slot.

I do have plenty of PCI slots though. Is there any disadvantage to using a PCI sound card instead of a PCI-E one?

 

[SlyReaper]

But a long PCI slot does deliver enough power?

I was originally going to get a xonar DX, but as I said, I'm not certain it will fit in the available slot. So it looks like the xonar D2 might be the one to go for.

Anyway, even if the card does require extra power, can't you get molex -> whatever power adaptors for it?

 

[SlyReaper]

Okay, final question: how much bandwidth does a PCI slot have compared to that of a PCI-E slot? And do sound cards use all of it?