Considerations:
- I play World of Warcraft pretty heavily (I have a G13 game pad and a G700 gaming mouse, so "G" or macro keys not needed).
I also play WoW. Honestly, any keyboard fits here. Unless you're looking for features when...hey, you shouldn't be taking your eyes off the screen either <stealthed rogue>
- Need a number pad but am willing to also invest in a dedicated number pad.
If you NEED a number pad, then it's a little bit different than investing in a dedicated. Would the price be the difference? A cheap TKL + tenkey pad vs a full size?
- I sometimes need to use Ventrilo (verbal chat room) and use a (Samson Go) desktop mic.
Not sure where a keyboard would fit here. Even really big keyboards still have room around them enough for a mic to be within distance
- I use Input Director KVM software.
This is actually a big one. Some of my mechanical boards had issues with my KVM (couldn't give you the model unfortunately). But my Cherry G80-3000 had this issue. Not sure why.
- I am a fast touch typist (was a secretary back in my IBM Model M days before going into IT).
So...a keyboard with keys. Got it

- I share an office with my husband. That said, we mostly are gaming when sharing the room and there are two gaming PCs running - not super noisy, but not dead quiet, either. Hubby claims a "clacky" keyboard wouldn't bug him.
I haven't met anyone who was personally annoyed by hearing a keyboard. But if he is, it might be good you stick with a switch you can eventually silence. Like Topre, Cherry (not blue), or Alps. Or Buckling Spring..you can silence them quite a bit, with little effect of the switch itself.
- I prefer something back-lit since I often game in a dark room, but can live without it if it means getting a superior keyboard otherwise.
That can narrow your options quite a bit, and also drive up the price.
- Would like to be able to change caps.
Cherry is the switch with the largest aftermarket for keycaps. You can get Topre switches but keycaps are expensive. Buckling spring the selection is limited (with really only variance to color, and no letters)
If not required, that can broaden your selection.
- Needs to have decently long cable(s) or be extension cable friendly
If you get a board that has a modular cable, you can get whatever size cable you need. Extending a USB board is rarely an issue.
- I would prefer to spend less over more (don't we all), but definitely under $200.
Fair. So no HHKB's or Realforces unless they're used.
With all this said, Cherry switches (not blue) would be easy to silence if the sound is an issue, and the range of keycaps are very wide and cheap. And most boards are made with them. A lot of Cherry boards come with backlighting, which isn't a deal breaker for you but a nice to have.
http://www.amazon.com/CM-Storm-QuickFire-Mechanical-SGK-4020-GKCL1-US/dp/B00A378L4CThe Quckfire TK offers backlighting, numpad (with integrated arrow cluster, read more about it), and media keys. It comes with a detachable cable, so you can get whatever length you're comfortable with. CoolerMaster also offers a Trigger which is a bit bigger. You can see the specs of each of their boards
further down on this pagethe only thing the CM Quickfire series doesn't cover is the open question about KVM's, you'll definitely need to research that. I'm sure there's more boards, but thats the only one that comes to mind.
You can also try your hand at your standard decently-built Leopold TKL's. They're a bit cheaper than Filco's, so it'll give you a little bit of budget to add a numpad.
http://elitekeyboards.com/products.php?sub=leopold,tenkeylessAlso, you mentioned being able to use your desk mic. If form factor is a requirement, there are a lot of smaller backlit Cherry boards available. But you typically sacrifice a number pad, or arrow cluster, and requires a slight adjustment. My girlfriend uses a Poker, and plays WoW. She doesn't miss the arrow cluster at all, and she never really needed to learn the "activating arrows" portion. So it all depends on what you're comfortable with.
Good luck, and hope you find the right board!