Question for the EXO Pack users. I am currently using an EXOK2 3500. The pack has been awesome as a good all around pack, but on multi-day back county hunts it is just a little too tight for my shelter, sleeping system, meals, etc. I have been contemplating making the jump to the EXO K3 6400, but I can purchase the K3 6400 bag for half the price and EXO says it will work on my K2 frame. My question is...is the full K3 pack that much better than the K2, or should I go the half price route and just order the K3 bag for my K2 frame saving me $300+?