I have the Premier and it is great only real gripe I have about it is it has a steering remote that I really hate. I sould of rather had the credit card remote that comes with the 8400
I had a pioneer premier and i didnt like the sound quality that came out of the deck. but if you still like the pioneer i agree with the other guys go with the premier it will last longer.
there are so many factors taht can affect SQ. now unless he had used a different brand HU and listened to it and then put in a pioneer HU and listened to it...then theres no real way of comparing. i had a alpine cde-7859 and i now have a premier p740 and i can tell a huge increase in SQ. but then again....what is SQ anyways??? everybodys ears are different and different sounds appeal to different people. its not like spl and can be metered. as a matter of fact i just read that some guy on here liked the rattles of his trunk when the bass hits. so to him....good SQ consists of rattles.
i had a priemer and i think that it didn't sound as good as a panisonik or an alpine (all three where hooked up to the same amp and speakers.) but sq is an opinion matter so what ever you think sound the best
the most difference I could get out of any hu was my 7 year old Sony mobile ES and Denon's A-1. There was a difference. THere's also a whoppin' price difference.
I like the 8400 a lot. I saw it while purchasing my changer last night. Wanted to do away with my old sony and get myself a new hu... couldn't do it, didn't have the balls nor the cash.
I own the 8400, and I love it, its a great headunit, especially SQ wise...(to me at least ;-)) so if you are looking into a new one I'd recommend that one, you won't have any regrets.
The only thing I regret about it is not getting the Premier 940...I don't know why but I started to like that one better...but thats all visual appearence. I still like the motorized flap face so I'd say go with it, you'll be happy.