Illustrator :: Exporting Graphic Styles

I'm designing a game for iPad and am using Illustrator CS3 to create the graphics. I created lots of card sized graphics and gave them all the 'RGB Parchment' graphic style which comes with Illustrator.

The document in the picture is (part of) an illustrator file that I created these cards in. If I take one out to another document to edit it and save it as a .png - it comes back different. As you can see in the picture, in the centre are two mock ups I made for a card. The left is an illustrator file 'placed' in the document and the right is the same file but exported as a .png and then placed in.

The .png keeps the transparencies but the shadow is completely different, it's a horrible brown as well as the shape being slightly different and the quality quite low. I sent the whole mock up picture (which is much bigger) to my iPad and I can still see the lower quality in the right, .png card.

If I want to bring graphics into some software to build the app I can't bring in illustrator files so I cant to create them as .pngs but when they're so different / low quality I don't know what to do. I just want to be able to use that 'RGB Parchement' graphic style and not have it changed so much when I export it.