Good luck w/Alpine install and please let me know how it worked out!
According to the Sales consultant with whom I have reserved my prius at least (on wait list), a custom audio wouldn't negate a warranty - but i'll have to confirm that now, def.
I'm planning to go with a professionally installed audio package of: Sony deck mated to XM receiver, front components, rear door 2-ways, 4x50w Memphis amp and 10" sub. It will be a big hit (quoted at just under 2g, complete), but I want a high quality sound and nothing less and if anything should increase the value of the car too if/when I trade in..
Plz let me know how your Alpine is working out! cheers.