sensitive and powerful PC to transmitter keyer

Hi, I want to see how simple a keyer can be made, sensitive enough to be driven by the audio of the PC sound card, but powerful enough to switch power into a 300-500mA 12v requiring CW transmitter.
My goal is to have the least discrete components possible, I do not mind if they are SCRs of custom-wound toroids or small commercial audio transformers.
The circuit to key is this http://qrp.gr/easy40/index.htm and I do not mind about "key clicks" in this simple circuit.

I would use a P-Channel MOSFET with the gate driven by an NPN (I'm too lazy to draw a schematic, but I will if you don't get what I mean). Your pc output drives the NPN base; the NPN collector is tied to the MOSFET gate.

Can you get a DC level out of your sound card? If not, you'll have to have some kind of filter on that signal.