Hi Cherry,
#1 Yes, you can sell directly on eBay as well as on Auctiva. Down the road we will be adding the feature to enter ISBN/UPC numbers so that you can sell your CDs, books and other types of items like this through Auctiva.
One thing to note about listing on both sites, if you have Auctiva checkout turned on, items that you list through Auctiva will direct the buyers through our checkout process to purchase the item. Items posted via eBay will go through the eBay checkout process.
#2 With Auctiva checkout, a buyer can not currently combine two purchases together. We've been waiting for eBay to provide this support via their API that we use. We were told this would happen in Q3 of 2005, but have yet to see anything. If they don't add this soon, we'll have to develop our own system of combining invoices.
Yeah, you wouldn't be able to purchase insurance on the combined purchases right now. That will come as we solve #2 above... for now you'd have to purchase insurance seperately or just on one of the items.
-Kevin