How to wirelessly trigger both a Nikon speedlight and a studio monolight?

I've got an sb-600 which I almost regret purchasing, and am planning on picking up an sb-2x sometime in the near future. I'm also thinking about getting some monolights later on, either some alien bees or possibly even a couple of einsteins. My question is, what wireless trigger system will allow me to fire the speedlights now and be monolight compatible down the road? If I have to grab a few pc adapters for the D90 and the sb-600, that is not an issue. I'm just extremely new to this whole manual wireless off camera lighting and have no interest in wasting my money on triggers that I'll only have to replace down the road. Thanks in advance.

Added (1). I'd like to stay away from pocketwizards, if at all possible. I'm obviously not a professional and honestly don't need them. Lets keep it cheap please.

There are less expensive units than the Pocket Wizards, but not nearly as inexpensive as the Chinese radio triggers. Believe it or not, the cheap ones last quite a while. I've had mine for a couple of years now, still work just fine. And if one fails, it's cheap to replace.

Look for triggers that have both a hot shoe AND a PC socket. Not all do. With those, you can fire off both hot shoe flashes like your SB-600, and flashes that only work off PC cords like the Alien Bee's. I do this with an old Albinar flash as a backlight, and two Metz 45's on stands, using three of the cheap Chinese triggers. The on-camera trigger and 3 receivers cost me all of $45 or so.

The Yongnuo RF-603s (get the version for the D90) work well. They are manual, but you will want to be in manual anyway for your studio lights.

Each RF-603 is both a transmitter and receiver, and you can use them for either purpose. And you can use up to 8 of them together, so select one for the transmitter and put it on the camera and then the others on each of your devices.

They cost about $25 for each unit.