I have a 2 channel set up. What is the best way

How would the 3 channel amp connect to my integrated amp?

To work as I've suggested, your integrated amp would need both "pre-amp out" and "pre-amp in" jacks on the back panel. The signal from the "pre-amp out" on your integrated amp would have to be routed through the Technics surround processor, and then back from the processor to the "pre-amp in" jack on the integrated amp. Then, the integrated amp would be used to drive your front speakers. The surround processor has additional outputs on the back that go to the 3-channel amp that will drive the center and surround speakers.

While the surround processor is engaged in the circuit, it will decode the 5.1 signal, feeding the decoded signal to all 5 speakers, plus a subwoofer (if you have one). The surround processor also has an output on the back panel to drive a subwoofer, but if you have no subwoofer, you simply program the processor for "no sub", and it will feed the full-range signal to the main front speakers.

Thanks for the tips. How do you feel about doing this with a A/V receiver. My brother has a A/V NAD receiverto sell to me for cheap. My integrated amp has the in/outs that you said I need to have.

An HT receiver is a good way to do this. You don't need a three chanel amp this way. Make sure the receiver also has inputs and outputs for the main channels.

With the receiver, if it has pre-outs for the main speakers, it's a bit different. You would keep your analog/music sources (CD, LP) connected to your integrated, and connect the video sources (DVD, SAT, VCR) thru the receiver. Run the L/R mains pre-outs from the receiver to an auxiliary input on the Rega. When you calibrate your HT surround levels, mark/memorize the volume setting on the Rega, and always return it to that position when listening/viewing material thru the receiver. You can do the same thing with a surround processor and external amp.