Where is the best place to go for inexpensive aftermarket accessories for my 2006 XB such as the upgraded tail lights, floor led lights, rear spoiler, etc? Thanks.

I have not found just one place to get All that stuff. I got my Head and Taillights from Ebay. My floor light are from a Computer mods website. So, if you don't want to pay the big $$. then you're going to have to do some foot work.

for the tails and the spoiler, check ebay for seller called toyotamall1 - great stuff.
http://stores.ebay.com/SCION-WAREHOUSE-TOYOTA-MALL

for lighting, oznium.com

Here is a good place for many xB things http://www.ssuperstore.com/ and yes, Oznium is awsome for lighting things

for the tails and the spoiler, check ebay for seller called toyotamall1 - great stuff.
http://stores.ebay.com/SCION-WAREHOUSE-TOYOTA-MALL

for lighting, oznium.com
trdsparks.com kills their pricing