one other thing

also asked that i wanted to add a sub and could i do it anywhere without affecting warranty

was told that i would have to have it fitted by lexus if i wanted to keep warranty

is this correct?

When I was looking at fitting a Sub, i would have to have 'tapped' a ignition power wire for the amp, so that the amp was only powered when the ignition was switched on.

I imagine that this would invalidate the electrical warranty, but it's probably worth waiting for an answer from an expert....