SACD *can* play surround but there are also 2.0 mixes. Every 5.1 SACD can also but downmixed to stereo on your home equipment. To people wondering what it is, it just sounds better than CD. If you'd really love to hear PF clearer than you have before this is the way to do it.

CD Frequency response - up to 22kHz
Vinyl - mmmm around ~30kHz, each setup is different depending on conditions of vinyl/toner
SACD/DVD-A - just under 100kHz

Simply put if you think CDs sound fine then stick with it. If you'd like to hear more, comparable to going out and hearing a live performance at a concert hall, then spring for SACD.

I'd wait until September to buy an SACD player. There are a buncha rumors concerning an SACD II format. Personally I'm waiting for some official statement to be made before I buy a player.