Yes, you can go from the red/white analog output of a 612 to the input of amplified computer speakers.
There are two digital audio outputs on the back of the 612. The HDMI output, which some folks feed to a surround sound receiver before going on to the TV, and the optical SPDIF jack. I've seen a few computer speakers that can accept SPDIF optical. If yours can, then just buy a toslink fiber cable and you're done. Otherwise, that too will probably need to get fed to a surround sound receiver via fiber cable.