You start with the Artificer's Metamagic Spell Trigger ability. The important thing to note here is that, unlike a similar feat, this ability doesn't impose any restrictions on how many metamagic feats you can apply to the spell at the time of casting so the more charges the wand has the merrier.
Before the really sick stuff begins you need to pick up the Cull Wand Essence feat. This will allow you to substitute a 4th level spell in the wand for very decent ranged touch attack.
Now, this is where things get really ugly, you can still apply metamagic feats to the ray. So, what you do is you take the Split Ray feat to double your fun, Maximize spell for obvious reasons and, if you really mean it, you can take Quicken spell as well.
At this point, you have a devastating attack that uses up a fair number of the wands charges (16 I think) in exchange for 240 points of damage. This damage is divided evenly among two 4th lvl spells that each have 2 rays that deal 60 damage on hit.
The next step in improving this killing machine is the Duel Wand Wielder feat. You need to take Two Weapon Fighting first but trust me it's more then worth it. Now you can deal 360 points of damage divided among up to 6 targets.
The final piece of the puzzle is the Belt of Battle. It can be found in the Magic Item Compendium I think. Long story short, once a day the item can give you a extra full round action. That adds up to about 600 points of damage in a single round.
Free action:
120 dmg from the use of your primary wand (60+60) / 11 charges
1st Full round action:
120 dmg from the use of your primary wand (60+60) / 6 charges
120 dmg from the use of your secondary wand (60+60) / 7 charges
2nd Full round action:
120 dmg from the second use of your primary wand (60+60) / 6 charges
120 dmg from the second use of your secondary wand (60+60) / 7 charges
For the finishing touch, suppose that you do this with Enervation spells. No saving throws, no nothing. Just 40 negative levels right in the kisser.
For your convenience here is a short list of the feats and items you will need to pull this off:
FEATS:
Maximize Spell
Split Ray
Quicken Spell
Cull Wand Essence
Two Weapon Fighting
Double Wand Wielder
ITEMS:
Belt of Battle
Wand of Enervation
Wand of Enervation
I'm too bored to read up the specifics to see if your right, but by the look of it..... *drools*
Wand Surge
Magical Artisan from Faerun for wands. It doesn't stack prettily, but it does give you some nice reductions.
Enervation and the Cull Wand Essence feat allow spell resistance and your wands will have a caster level of 7th (possibly 11th, I think there is a feat that bumps up caster level) with each wand costing you 21,000 gold a piece. Even at half cost for crafting it yourself, that's around an eighth of a 12th level character's wealth for each shot, with a good chance of it not bypassing spell resistance and still requiring a ranged touch.
Easy things first, I honestly don't think that hitting with a ranged touch attack is such a big problem. You have a decent attack bonus, will have at least a +2 bonus from Dex. To hit most things you will only need to throw 5 or higher on d20. Also, in the example I made above it doesn't really show but you are actually making 10 ranged touch attacks, two per wand activation. Hitting with even half of them will do just about anything in, be it through damage or negative levels.
Spell resistance is serious on the other hand. It might be important to mention that the caster level of spell trigger items is determined at the time of their making, it just costs money. Another thing you may want to do is to first use to start the draining chain with a staff with similar properties and when the target has been sufficiently softened-up proceed as normal.
As far as the costs are concerned, you take the Warforged as your race of choice so you can take the Warforged Artificer substitution levels at 1st and 4th lvl. Following that you take the Legendary (items cost less exp) and Extraordinary (items cost less gp) Artisan feats. With these feats and racial/class abilities it's highly unlikely that you will ever run out of EXP to refill any wands you might be using. Even if you just stick to making one +1 longsword per day you should still be able to make a profit and an even greater gain when it comes to your craft exp pool. Taking a +1 weapon as an example it looks like this:
Item creation costs: 750 GP (75% of the normal cost), 30 points from your craft pool (75% of the normal amount (60) and your racial substitution level halves that number).
If you decide to sell the item you will earn something over 1200 GP for a two days work. Alternatively, you can drain the item for 80 craft pool points. Anyone see where I'm going with this?