You can't listen to multi-channel SACD's on one pair of K1000's...but two pair, now you're talking. And yes, you'll need some sort of prepro to redirect the 5.1 to 4.0 channels.
So: no, absolutely not, I would not get a multichannel SACD player to play multichannel audio on K1000's.
However: I would recommend getting a SACD player for the higher fidelity. I listen to my SACD player exclusively two channel, and it's worth it, even if occasionally.
Here's the thing: Sony has an inside edge on SACD's, so for entry level, they're impossible to beat. For CD's, I would still use an external DAC. This is my setup.