When I swapped my LT's speakers this summer, I got slightly upgraded ones for the rear, Alpine SPS-13C2 5.25" 350 watt 2-way, aim-able tweeters, poly cones (not affected by water, but don't soak 'em). I chose them after researching crutchfield--4.5 out of 5 stars, and their tech guy said they would be a good fit--and a couple stereo websites)
Bought them off of EBAY, do a search on ebay for:
west coast electronix
their posted email is:
they've had the speakers on "buy it now" for $39 a pair, and about $26 for shipping all summer...if someone beats you to the one listed, drop them a line, they always have them in stock.
ANY of the EBay sellers that have them for under $45 and under $25 for shipping as a "buy it now" will do you good...you don't have to mess with bidding, etc.
(PS...Best Buy has them "on sale" this week for $95.99 a pair, crutchfield for $89.99, add tax and shipping to that...)
I have had mine since July, am still very impressed. If you want to spend more, help yourself, you can also buy an additional cross-over amp, jack your system up to about 6,000 watts, and put in the latest from Snoop Doggy Dogg, and initiate forward momentum without even starting your engine.
(in other words, this is just ONE option for upgrading your speakers, those with more money are welcome to look into pricier options, you can feel absolutely FREE to post your solutions to the "OEM speakers don't really cut it" issue here, but it won't be necessary to rip me for my choice...I bought four really decent speakers for under $120 with shipping and it made me happy so
If you take a look at my post from a while ago, I threw up a snapshot from the service manual showing how to replace the front speakers, and talked about how I, um, "modified" the tabs to make it fit. Haven't had any vibration problems or any others in the front, and the rears fit perfectly--if you look at the files section of the forum, I posted a document with step by step and lots of pictures, too.
Good luck, and enjoy the better sound.
Pete "Pimp my LT" Van Dyke