PC Speakers for Home Theater System?

Okay, here's my question. I recently bought a set of Megaworks 6.1 THX Speakers, so I have no issue whatsoever with sound on my PC. However, now I have my Altec Lansing 5.1 speakers connected to nothing which seems a waste.

Now, my brother recently moved into a new house and bought a 52" projection screen T.V., and has a pretty nice stereo speaker setup. Now, does anyone know if there's a good way to incorporate my Altec Lansing speakers into his system? At 140 watts peak, I think they are definitely underpowered to be used as a home theater system in and of themselves, especially considering his living room is around 300 square feet with a twenty foot ceiling. But I was wondering if they can be hooked into his existing stereo or his TV, so at least he can use the subwoofer?

Sorry if this is a dumb question...I know next-to-nothing about audio outside of the PC world.

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