If you had the int to take Expertise (there are magic items to boost Int), Weapon Master (S&F) is a great class to aim for if you are looking for going the smackdown route. The have a whole bunch of really nifty features for that sort of thing, such as Ki Whirlwind, where you can do a whirlwind attack as a standard (not full) attack action. They also have a whole bunch of feats for increasing your crit damage. The downside, is that it requires a ton of feats (6) to qualify.
Master Samurai would also be a good combat choice, but somehow it doesn't sound like it would be a good match to this sort of character. However it is a better match in terms of feat selection (and stats), but power attack and cleave work very well with the whirlwind attack feat chain you'd need for the Weapon Master. Most of the extreme fighter smackdowns involve some sort of cleave/whirlwind attack combos.
For weapons, you want something with a wide crit range (at least 19-20) to get the maximum benefit out of Keen and Improved crit. That's one of the reasons why Greatsword is a classic for barbarians. There is also a "Power Crit" feat that will be in "Masters of the Wild", odds are that it is to improve your crit multiplier (ie. to go from a x2 to x3 crit). Actually, it looks like there will be a lot of cool feats in MotW and you are well placed to take advantage of them.
When you get your weapon enchanted, make sure to go with a "Burst" weapon, the extra D10s of damage dovetail nicely with the enhanced crit range and crit mods. Particularly if you stay with some of the x4 crit weapons, you'll be getting +3d10 on crits.
A couple of levels in Rogue are also quite useful both for the skill points and the sneak attack damage + evasion abilities.