I agree with Johnss - both SACD and DVD-A offer a dramatic improvement over Redbook CD. I think it depends a lot on your system though. For me, since installing Theta Enterprises, the difference is just huge. And FWIW, I find Multi-channel not worth much of my time. I do almost all of my listening in 2-channel in spite of being close to ideally set up for multi-channel.
Regarding a player, it is very much dependant on your budget. Right now I am using an Upgrade Company modded Denon 5910. It was an improvement over my Upgrade Company Esoteric DV-50 that was noticeably better than the venerable EMM Labs CDSA-SE. I would wholeheartedly recommend the very same player since it is so good on all formats.
And as far as being a niche product...so is vinyl. Once you begin to find companies such as High-Res and outlets that specialize in DVD-A and SACD (Elusive Disc, Acoustic Sounds, AIX, CD Universe, Music Direct
), the number of titles does increase somewhat. Still, don't expect to find much locally. All of my SACD/DVD-A discs are bought via internet/mail-order...the same way most people get their vinyl.