Did I just mess up buying a headunit?!?! HELP

http://www.bestbuy.com/site/olspage.jsp?skuId=7660541&type=product&productCategoryId=cat03066&id=1134701325185
^^headunit I just bought
http://www.audioallies.com/getitem.asp?Item=KDC-MP4028&Sys=FR
^^headunit I had before

I just got a new headunit today to replace my old one which had broken. The one I had had front rear and subwoofer preamps (3 pairs? of 4v im not sure I'm new) and the one I just bought has 2 pairs of 2 volt preamps for connection to separate amps. Thats what it says. Am I going to notice any differences and not be able to control as many features. I have an amp and subwoofers also. Will my new one control them all the same as the old on? Also what does the voltage mean when related to preamps? I'm new so sorry if this is all obvious. Should I bring back the one I just bought and wait for http://www.bestbuy.com/site/olspage.jsp?skuId=7675599&type=product&productCategoryId=cat03066&id=1134702498186 this one which was temporarily out of stock?

you've only got 1 amp... you're fine. you don't need 3 pre-outs.

so I'd only need more if I had 3 amps? since I have 2 preamps. Thanks Im understanding that more now I think haha. Do you still think I should keep the Kenwood over say the Panasonic even tho the Panasonic has Subwoofer crossover and Output control? as well as Aux output or do those 2 options not really matter/effect anything? Also does the 2v or 4v preamp matter?
http://images.bestbuy.com/BestBuy_US/images/global/misc/spacer.gif

get the one you feel will be the most comfortable to use.