pioneer headunit preamps

I am trying to decide which headunit to go with. The pioneer deh-p6600 or the deh-p7600. There is about a $50 difference at BestBuy which I have giftcards to which is the only reason I am getting it from there. The only difference I could see was the 7600 will play MP3's and WAV and the amp preouts are 4V. whereas on the 6600 they are 2V. What I wanted to know was if this 2V difference really makes a big difference and makes it worth $50 more. I already have one alpine amp running my front stage and will be installing a Hifonics Zeus ZX4000 to run my new Shiva Sub, if this info helps.
Thanks, Aaron

what headunit do you have now and how strong are its preouts?

Currently I have the Pioneer DEH-P7300 which I believe is the older version of the 7600 and has 3-4V. preamp outlets. The only reason I am replacing the headunit is because one of the connection copper prongs broke off from the main unit so there is no display whatsoever so I can't see to make adjustments to levels.

if you pause the cd player and have no background noise or hiss, then you should be fine with 2V as long as you set the gain properly. Look at the differences in the actual features to decide if the higher model is worth $50 more, don't look at the strength of the preouts.