Ok...I'll bite.

IMO, the #1 component is defiantly the room.
I've got great speakers...and they sound like crap because of my room.
I will quote from something else I read recently; "a great room can make
a marginal system sound magical, and a bad room can make a great system
sound horrendous".

Not verbatim, but you get the idea..and it is true as I've lived both
ends of this spectrum in the past year.

in my last house, I ran a system I put together for $1200. It was the
cats ass. Completely pleasing and then some.
In my current house, I built a system costing 5x this...and it is
nothing but frustration. Again, the room is putting all of my upgraded
components and speakers to waste.

My other rule of thumb is "crap in, crap out"...so source and material
are high on that list.

I'd go:
1. room
2. speakers
3. source/material
4. amp

and I'd leave it there as a premap is just not even necessary in a
purely digital domain...which is where I live. If you are listening to
LPs and tapes, then i'm sure it has a place on the list.