I have a KX3 (using I+Q) connected to my RPi listening to WSPR on 40m tonight. I don't have the cat controls working yet but I will probably tackle that after I install FLDigi. The RPi has no performance issues receiving and decoding WSPR. The CPU jumps up to 70% for a couple of seconds for the decode then goes back to under 20% during receive.
Pretty cool (and geeky) stuff.
73 de NG0R