Which link is most important?

I don't agree with Gregm completely, I always found better results working upstream and flowing down, i.e. start at the source and go to the pre THEN go from pre to amp, what's lost can never be regained and for that matter any coloration added between the CD player and the pre will be amplified through the pre- one sure way to find out is to listen yourself :)

T-guy: I agree. But since there's only one set of IC, I thought the improvement (one way or another) would be more noticeable if the experiement was conducted in the order I recommended. Cheers!

"All things being equal", if you use more than a CD player, putting your best cable between the preamp and power amp will improve the performance of every component plugged into the preamp. CD players tend to picky on cable choice from my experience, so if you are going to demo some cables, try many with your CD player.

For inexpensive cables, you can't do much better than the MAS cables made by Stu Wein of Audioparts (his screen name on Audiogon and eBay). Stu can be contacted through Audiogon and has many cables listed currently. He will custom make cables anyway you want. He has various grades/quality of cables... See this link....

http://cgi.audiogon.com/cgi-bin/search2.pl?seller&zzAudioparts

smaller signal is more vulnarable to the wire quality so the cd-to-pre is the right decision.
if you have Sam Ash music store near you i would suggest to pick up canare japanese cables for the price of RadioShack wires or even cheaper with absolutely great performance comparable with budget AudioQuest interconnects such as SideWinder.