The 80GB Playstation 3 plays Blu-ray, CD, DVD, and SACD. You can get a Toshiba HD-A3 or HD-D3 for about $179 that plays CD, HD DVD, and DVD. Both units upconvert std. DVD very well.
So if you have the shelf space and room for the I/O connectors, you can get HD DVD, Blu-ray, CD, excellent upconverting DVD, and SACD playback capability for a combined $679, but not in one unit. I already have a Toshiba HD-D2 and am seriously considering a Playstation 3 to handle Blu-ray and SACD. The Playstation brings some advantages here, such as a smaller footprint (13" wide) and so much internal processing power that it loads quicker and plays more glitch-free than typical standalone Blu-ray players (according to reviews I've read).
If you want hi-def video and DVD-A, I believe there's a Panasonic Blu-ray unit that plays both, but not SACD.
Another approach might be to get an Integra 9.8 pre/pro or Onkyo AV 705 or 805 receiver. Then you could get an Oppo DV-980H, a Toshiba HD-D3, and a Playstation 3 (you could save $100 and get the 40 GB version because the Oppo plays SACD and DVD-A), connect them all with HDMI cables to the Onkyo unit, and the Onkyo unit would extract all the hi-def, non-compressed audio. Even the Oppo sends the full datastreams from SACD or DVD-A via the HDMI cable.
In this scenario, the only limiting factor is your shelf space. But you could use 12- or 15-foot HDMI cables and set the disc players elsewhere. You can get 12' HDMI 1.3-spec cables for $20 or less.