Appropriate RCA cable to go from pre-out to amp?

I'm in the same boat--about to replace my integrated amp's jumpers with an IC. I was just reading a thread on another forum in which several people opined that the pre-to-amp connection is the most important and most sensitive. Which is it? and why?

Elizabeth,

my one and only "new car" was in 1978, around the time I had a Mac 2300, C-28 and 2 pairs of ML-1 loudspeakers. In those days mainstream audio (and none more mainstream than McIntosh) didn't seem concerned with IC's and such. '78 was also the year I started out as a music teacher and sealed my fate, financially speaking. Not much disposable income for electronics.

For all the power I had with that rig, I did not find the speakers to be especially accurate or revealing (though they could sure "thump"). Now I have speakers I like but little power. I expect that if I boost the power I will find that in addition to better IC's I will want a better preamp as well (will probably use the pre section of the NAD initially).
Kooshballa, congrats on solving your problem--I'm sorry for temporarily diverting your thread a tad.
Am still interested in hearing exactly WHY anyone thinks the pre-to-amp connection is more or less important than the source-to-pre connections. Maybe another time...?