Check this clip from an early episode... Buffy appears near the end. That is definitely a Sideshow Buffy, and I've seen several others as well.
You are right that is the SS Buffy with the crossbow. However the girl on the left in the scene after that is the 1/8th scale custom SMG. Can't tell from the preview about the Qui-Gon. The body movement looks like the custom foam body they use for animation, which is 1/8th scale from what I've read. Last season they had a custom of Liam Neeson as Ducard from Batman Begins that was a dead on the money likeness. Could be they moded that, or maybe they have a new body. Sometimes the stuff flashes by so fast on the screen it's hard to tell. A lot of people (myself included) assumed that the Napolean Dynamite head from a season one episode was from the Macfarlane figure, but it was also made by PE. The PE website has pics of heads they have done, must be close to 200 different sculpts. I couldn't believe that most of the sculpts were done in less than 8 hours. Would love to see what that company could do with a 12 inch figure line.