Well this morning I got my cable basket out and tried several different ICs between portable CDP and Grado RA-1 amp, easy matter to switch. Using the gold Radio Shack Mini/dual RCA plug I quickly tested the following:
HomeGrown Audio Silver Lace, $190 meter
DiMarzio High Definition, $90 meter
Analysis Plus Copper Oval, $260 meter
Harmonic Tech Truthlink, $250 meter
Most of these can easily be bought used at Audiogon, sometimes at 50% discount. Actually the $25 Straightwire unit from headroom held up very well, partly because as Mario points out
a portable has much reduced resolution over full size CDP. The only combo I thought was noticeably better vs Straightwire was the Silver Lace, but it was not a big improvement. If I didn't already have a set I wouldn't buy a set just for portable, I would settle for $25 Straightwire cable and be happy.
Also many of these ICs are thicker and stiffer, and can cause set-up problems with a portable and small amp, another reason to stick with straightwire.
Do explore isolation devices for portable to set on. Try foam, bubblepack, vibrapods etc very important to eliminate as much vibration as possible here, cost is minimal.