will I have to have a 5.1 system to enjoy the DVD audio side of the disc? Or a special player?

I guess I'll look for a Vintage Quad receiver on ebay if so..

No special player is needed for that disc - it's just 5.1 Dolby Digital. You could play the DVD side on a 2 channel system, but you would lose the benefit of the surround, so you may as well just play the CD side for the best fidelity.