I'm happy with my 4.7L, it really has more than enough power for daily driving and having some fun. It will also tow your 4000lb with no hesitation. The 5.7 is just even more power and mainly for extremely heavy towing. I wouldn't hesitate to tow 8,000lb with my 4.7L (although at that weight I'd probably wish I had the hemi). I also have the superchips on mine which really makes a whole world of difference. When stock I was averaging in the 16's for gas mileage and now with superchips I average in the 17's, but if I go all highway and keep it at 70mph I get above 20mpg (got 22.5 this weekend on a 4 hour trip). I'd say if you want the hemi, look for it, but don't let it be a deal breaker, the 4.7 is a great engine and sounds like it'd fit your needs.
Breathing in and out is good enough for me.