I definitely checked under my trunk lid on my CompG 04 GTP. The WS6 RPO code is there. I'm really enjoying the car. The tapshift is fun and is taking some time to get used to. The car is very quick to respond to turns.
I do wish there was a memory seat option. It does take me a little while to find the right sweet spot.
One advantage is that the 2003 is eligible for the $3000 off, while the 2004 is not. I think the new look and "reach" is worth investing in now if you're not concerned with the lack of side airbags. I haven't had side airbags in any car as of yet so I don't know what I'm missing.