I've got a 2006 Grand Cherokee SRT8. Love it. It's got the 6.1L motor, plenty of power for the family hauler. Full time four wheel drive. Easily fits me, wife and two kids (14 and 7), and still able to load things in the cargo area.

I had a 99 inline 6 4wd and a 2004 4.7 HO AWD. The power of the 04 was great but the reliability of the 6 can't be beat. You see people getting 250k + out of the 6 without any major engine work. You won't see that in with the 8. We had a bunch of problems with the 04 as did friends with the same engine.

The straight 6 is one of the best motors ever made in my opinion, it's bullet proof! My 90 and 98 Cherokees as well as the 01 TJ all had the six with zero issues, I sold them at 180k to 200k miles and still got good money. They make killer stokers as well. Both of my Grands have had the 4.7 and so far so good. The tranny in the older one gave me fits but never a hick up from the motor. The 4.7 was also used in the Durangos and Dakotas, I've heard and read stories but have had good luck so far with them.
With that being said, I'm loading up and heading out for the weekend with the family...over two very snowy passes...in the dark....maybe I shouldn't have said anything!