To do it right you'll either need to buy spacers or build them, this will open up a lot more speaker options. I thought the pre-made ones were a bit expensive, so I built my own out of MDF. A jigsaw and a drill are pretty much all you need. Total cost to build, about $10, took me a few hours to design, cut, and trim them. I've also heard of one guy who cut the speakers out of the stock spacers and used them to mount the new ones.