What is most important part of a system?

For me, the loudspeakers are the most important part of your system since. No matter how good your source is, if the speakers can’t convey the full dynamics, scale, impact and resolution as a coherent whole, with realistic sound staging and imaging, then you will never get the full capability out of a better source. Then again, I was ruined for life after hearing a pair of Infinity IRS-V’s in a Dealer’s showroom back in 1991!

Next in order would be..

- Source
- amp
- room-
- cables
- isolation
- a/c power
- good recordings

I used to think speakers, but my opinion has evolved a bit. My previous system (Linn speakers) seemed to sound pretty much the same irrespective of the amplifier and/or CD player; and most CDs sounded decent and similar. However, in my current system (Zu Def 4s) when my SET amp required servicing and I had to use a back-up SS amp, the sound became almost boring and uninviting and unengaging; it reverted to "normal" just as soon as my SET was re-inserted. Plus, CDs sound "different"- some good, some bad, and some indifferent. 

The room.

Speakers - 60%
Room - 40%