Getting the ghost-touch enchantment on your swords will allow you to reliably harm incorporeal undead; flaming, holy, and undead bane are good additional enchantments (the nightshades are the only undead creatures I can readily think of with fire resistance, but a 12th level party is no match for a nightshade, anyways). Though there isn't an actual proper undead-bane enchantment in the DMG...
If you have a LOT of spare cash, you can shoot for getting a Sun Blade, which actually handles just like a short sword (i.e., it's a medium-large weapon that handles like a small one), functions as +4 against evil creatures, and can apparently critical on undead (for x3 damage, no less), though the x3 crit ability is a lot less useful if it only works on evil outsiders from Negative Energy Plane (all one of them?).
A sun blade is worth 30,315 gp on the market..
Perhaps more reasonable, but very vicious, is something that goes for about 20000 gp, is a wand of Searing Light cast at 10th level -- a ranged touch attack that will deal 5d8 to the living, 10d6 to the undead, and 10d8 to undead that are vulnerable to sunlight, with no saving throw. And wands are simply a straight DC 20 UMD check to activate, which is also nice.
As a side note, while wands of cure mod. wounds are nice, ya can't really dual-wield them -- it's a partial action to activate a wand, so you can only do 2d8+3 damage twice per round -- if you've been hasted. And it allows a Will Save for half, which unfortunately is the one good save for undead.
Seriously, a bandolier of holy water vials could be cheaper and more effective than the wand. Or not; I just noticed that you don't have quickdraw, which sometimes surprises me with its ability to actually be a useful feat.
So if ya have the resources, bringing your swords up to snuff is what would allow to you do the most damage, and getting a ghost-touched mithril chain-shirt or breast-plate (and a ghost-touched mithril buckler) wouldn't be bad, either.
I hope that's of help.