SACD - Some are multichannel only, some are stereo only, some are both, and some are SACD/CD hybrids. The hybrids contain two layer substrates, one is SACD for compatible machines and the other is ordinary CD so it can be played in any ordinary CD player. Cost - expensive / Occurrence - rare
DVD-Audio - Use the DVD Video format but adds a special audio track that isn't compatible with ordinary DVD players called MLP Lossless. This audio format is basically high resolution multichannel PCM. Most DVD-Audio discs contain secondary 2 channel basic PCM tracks as well as Dolby or DTS multichannel tracks. Cost - expensive / Occurrence - rare
HDCD - Hybrid CDs with 20 bit and 16 bit compatibility. If your CD player has HDCD decoders it will utilize the 20 bit data stream, if you have the CD player connected via Optical or Coaxial to an HDCD compatible DAC, processor/preamp, or receiver, it will utilize the 20 bit data stream, in all other instances it uses 16 bit. This means if you connect an HDCD compatible CD player to a receiver via optical or coaxial digital that does not have HDCD compatibility, you will only get 16 bit. Cost - typical of normal redbook CDs / Occurence - common
FLAC - A lossless rip from another digitized source. This is a codec that is mostly used in the data world, via computers and can be stored on optical, hard disc, or solid state data devices. Unlike MP3s the data is completely uncompressed, so file sizes are larger and data loss is minimal to nill. Some people like to rip LPs to this format as well as CDs. This is especially convenient for LP rips because you can get very high quality rips from a properly setup turntable and recording device connected to your PC or MAC. Cost - cost only of original media you're ripping from / Occurrence - open availability
As was mentioned above with your player you'll likely get the best performance from using the player's analog multichannel outputs. Some receivers can process SACD's DSD (Direct Stream Digital) and DVD-Audio's MLP Lossless PCM if connected via HDMI.