After reading this thread & consulting Crutchfield's webpage, I bought two pairs of Pioneer TS-G1040R's (http://www.bestbuy.com/site/olspage.jsp?id=1067391222565&skuId=6195949&productCategoryId=cat03074&type=product). (added bonus is right now it's buy one pair, get second 1/2 off). They're 4" and fit perfectly in the dash and in the C pillar-meet-roof of my wagon. By removing 1-2 of the tabs, they can be fit into the hole in the dash and won't protrude beyond where the dash curves down towards the windshield. I don't think I can retrofit the original speaker's clips to the new speakers, so I will probably just screw them down into the dash (not a problem since this area is covered by the dash speaker grill). In the rear, MB has a different screw-hole pattern for 1/2 the speakers. The OEM speakers caem with standard screw holes and the "4M" holes; for the new speakers, I just intend to not screw them in at the corners where the holes don't align. Or, if I feel like I have time, I might drill holes into the speaker mounting plate to match the speaker. Also, NOTE WAGON OWNERS, the foam surrounding the original rear speakers gets sticky gooey over time. Some of mine fell onto the carpeted floor and has become a real headache to get out. Remove the speakers immediately once you've removed the headliner surround, and scrape off all of the foam before it destroys something you love. I plan on getting some house door-weatherstripping sticky-back foam tape to mount at the edges of the new speakers to replicate the original foam, which I assume was there to a)reduce noise dispersion into the cavity between roof & headliner b)keep the headliner surround properly spaced from the speakers.

I'd like to know from 300TDT hwo the aura bass-shakers work, if you installed them yet. I too want some more bass, but am not about to ruin the functionality of the cargo area with a bass box. A few manufacturers (clarion, kenwood, others?) make powered sub-like boxes that are only a few inches deep to fit under the seats, but they are about $300!