Those Crutchfield enclosures appear similar to what I have in my SL. I really wrestled over going with the enclosure solution for the rear speakers, but am glad I did. Sound quality is superb and it's little trouble to remove the speakers and store them in the trunk when I have need for the back seats or shelf.
Also, highly recommend
http://www.etronics.com as a good site to pick up speakersand other electronics. They have a wide variety of products and their prices are the best I've come across.