hi guys, this is my first post here so dont laugh if you think its stupid.

Ive been using a stereo amplifier all my life and i feel its time to upgrade to a AV amplifier system. So ill need to replace all my speakers as well with a speaker package. (main speakers + surround + active subwoofer). According to what ive been told (by shop assistants and neighbors) with regards to the subwoofer output of the AVamplifier, I'll need to use a DVD player with AC3 ouputs in order to activate my subwofer output on the AV amplifier.
Is this true?

the trouble is, i have a many devices that i still wish to use (tape decks and the like) that only have stereo outputs. and I'd still like to have the full effect of my speaker package.

if this is true, is there a decoder module in existance that will split my stereo signal into the respevtive AC3 equivalents, as i dont think it would be wise to feed the stereo signal as is into all the AC3 inputs of the AV amplifier