Which IC is more important?

I don't know if there is a definitive answer but I always found it better to work from the source down, in other words a great IC b/t your pre and amp will not make up for the radioshack b/t your cd and pre, however do not make the all to often mistake of using the audiophile equation better=more$$$

I'd say both are important in my experience. If part of the path is weak it will affect the sound. My best IC is between the Preamp and Power Amp for the simple reason that I also have a Tuner, Turntable, Tape Deck and Video Source plugged into the Preamp. Having my best IC as a pre/power link helps all of these components sound their best. It is a budget issue. My Pre/Power link is a Nordost Quattro Fil. I cannot afford more than one. My second best IC is from the CD player to the Preamp (Siltech). It has the biggest potential for improvement. A tuner only goes to 15,000Hz, so no need to improve the highs above that. Lastly, component matching is important. The "best" interconnect for each component is not necessarily the most expensive. It is the one that sounds best to me regardless of cost.

Also my REL subwoofer runs off the speaker terminals (high pass filter) so the best Pre/Power link also affects the bass signal picked up by the REL.

The source to pre IC carries a lower voltage signal so, the less the sonic interference of the conductor, the more "true to source" is the sound going to the pre. This said, different cables perform *differently* at different placements in the system (lots of differents here, sorry). Trial is the way to go -- another trick is to use the same cables throughout if you like the sonic signature (or lack thereof). The logical sequence would be, source->pre, pre->power.

BUT, cables performance in some systems is a function of system x voltage...

I, for one, would expect that Sugar's siltech/quattro combo is best as is, rather than the other way round: in my experience, the quattros were better with higher voltages. Sugar knows best, but maybe he doesn't need to afford a 2nd quattro.

I used the low to higher voltage sequence when assessing cable upgrades.
Cheers!