i have already installed a pioneer 3200bt touchscreen in my xterra and it sounded great for a while but the speakers are starting to sound like crap. so.. i was trying to decide between polk audio 6x9s or infinity 6x9s. or if someone has any other suggestions i am open to try new brands. i am installing them in the front and will wait to do the back. i was also wondering if i should soundproof the doors or would that be a waste of time and money. and what brand mat should i use. thanks in advance..