Ironically, I am working on pretty much the exact same concept right now. Weird...
So, my advice is this:
First, I wouldn't take any levels in monk. It's been my experience that they don't stack well with anything else, and unless you specifically want monk powers, it's a waste of levels. Half your powers don't work with armor or weapons, and your stunning fists will quickly become ineffective once you stop leveling up as a monk.
Even with a low-level flurry, you'd be better off with two-weapon fighting feats as a straight fighter. You'd end up with a better BAB, hit points, etc.
As was already said, don't worry about the martial staff- once you're power attacking for more than 1 point of damage, it's a wasted feat.
Using the PHB and Complete warrior, and if you want to go crazy, this is what you could do with this concept:
Power Attack: If you're fighter, this is mandatory, unless you want to be bouncing your 1d6+2 off of critters with damage reduction at high speeds at 10th level.
Two-weapon Fighting: because it's a double weapon, and you need to take advantage of that. Otherwise, it's a club that takes two hands. If you really want to embrace the concept, take Improved and Greater as you level up.
Two-Weapon Defense: It's a free +1 Shield AC bonus, which seems thematically appropriate for a staff-weilder. You can take Improved and Greater Two-Weapon Defense from the Complete warrior as you level up.
Alternatively, or in addition to Two-Weapon Defense, you can take Quick Staff from the Complete Warrior. It gives you a +2 dodge bonus when used with Combat Expertise, at a hefty prerequisite cost. You need the following: Dodge, Combat Expertise, Two-Wapon Fighting, Weapon Focus: Staff. Personally, I think I'd give one or more of the two-weapon defense feats if I took this, since it seems to be enough.
Combat Expertise: Again, in keeping with the theme. Always give up 1 from your BAB, and you'll get +3 Dodge AC when using your staff. Combine it with Two-Weapon Defense, and you get +4 AC, take all the feats, and max out your Combat Expertise, and you get +10 AC while still making a full attack. Of course, you're at -5 to hit, and more if you're attacking with both ends of your staff.
Dodge: Another +2 dodge vs. one guy, meaning a possible +10 AC in melee.
Weapon Focus: Staff: You'll need the +1 to make up for all the penalties if you're maxing out your defense (of course, nobody says you have to, this can simply make up for the -1 you're always taking to utilize your Quick Staff feat)
While you're at it, you can take:
Weapon Specialization: Staff, Greater Weapon Focus: Staff, Greater Weapon Specialization: Staff, depending on how awesome you want to be with your staff.
If you want to be a spinning fury of wooden death, you can take Whirlwind attack (and of course it's prereqs: Dodge, Mobility, and Spring Attack)
Improved Combat Expertise: I thought of taking this one to simply max out my defensive insanity, but this one seems a little unnecessary, unless you thing giving up +5 BAB for +7 AC isn't enough.
So, I've played with a couple different builds, one favoring two-weapon attacks, one favoring AC bonuses, and one with Whirlwind attack. Looks like you can't have it all, but you can probably find a happy compromise.
Dread Polack