I just replaced all of my speakers in my 01 Tahoe. It has the factory amp. I need to replace the stock subwoofer. I know it's an 8" and from what I read online it's a 2 ohm? My question is, do I have to get a 2 ohm or will a 4 ohm work ok with the stock setup? The 4 ohm subs seem to be alot cheaper in price.