From what I know, the pricing will vary quite a bit on this vehicle depending on the particular dealer/location, the individual sales person you're dealing with, the options you want, and the time of the month. I've heard it's harder to negotiate near invoice if you want one with the navigation system.
My own experience. When I first started shopping (last month), the quotes I got were all over the map, some as high as 2000 over invoice. I ended up purchasing my 2004 RX 330 (no navigation) on July 2 for approximately 200 over the dealer invoice, Central Florida dealer. I had lower quotes from two dealers (Countyline Lexus & Lexus of Palm Beach) in South Florida. I got my local dealer to lower his price showing him the lower quotes. His cost came to few hundred more, but I didn't mind paying the little extra to save myself the trip.
In California, I've heard the best places to shop are Longo Lexus (El Monte, Calif.) and (Coliseum Lexus, Oakland). My sister just purchased a 2004 EX 330 with the Mark Levinson package below invoice from Coliseum.
As for pricing: Be aware that your Lexus/Toyota dealer invoice will differ slightly from region to region (unlike other manufacturers), because of the different distributors Lexus/Toyota uses. There is an additional layer of pricing with mandatory distribution fees in certain regions/states (i.e. Florida).
I found a good place to check for an accurate dealer invoice is Carsdirect, because they also include these regional distribution fees (if any) in their quote. Put in the zip code of the area you want to purchase in. Also, you can check at Lexus.com (build your Lexus) to see the mandatory options packages, that come with the vehicle, in a particular region. Knowing what the packages/options are, on the vehicle, will help you to figure out the exact cost. Good luck.