Thought maybe you'd like to see the results (last pics are crappy, sorry):
Front passenger footwell:
Both front and rear passenger doors open, footwells lit:
Front drivers and passenger footwells from passenger side:
The neon tubes I bought (OptX by StreeGlow from Advance Auto or Best Buy) are really quite perfectly bright. The pics dont do it justice, it looks really really good in person.
To give you an idea of brightness, I had my lights on so the dash should have been lit up with the stock green backlighting and you cant see that in the pics. I'd like to say though that its not too bright by any means, its rather quite perfect for a really cool look
EDIT: I mounted 4 total 9" tubes. One under the drivers and passenger front seat (lights up the rear floor area nicely) and one under each side of the front dash. I fabricated a custom 90 degree bracket and used 3M double-sided super strong adhesive tape to secure the front two tubes up under the dash. The tubes are completely hidden unless you actually put your head under there and looked. I'm quite pleased!