By far power conditioning would rank first and foremost on my list. Simply because 'proper' line conditioning is so fundamental and foundational to the overall performance and listenability of a given system. It's still one of the final frontier's for many.
In fact, once you've experienced long-term listening with excellent line conditioners, you will discover that most every other system is quite fatiguing with grain, hash, negative induced siblilance, etc..
Note that I use the term 'proper' because, like any other component, there are plenty of line-conditioners that simply aren't worth much and in the case of even some very popular line conditioners the sonics are actually better when you remove the line conditioner(s) from the system.
Since my line conditioners have a built-in power cable, I consider them one and the same.
Beyond that whether the ics or scs come next might best be answered by first determining which of the current ics and scs is hindering performance the most. That would determine for me which will provide better benefit.
-IMO
In fact, once you've experienced long-term listening with excellent line conditioners, you will discover that most every other system is quite fatiguing with grain, hash, negative induced siblilance, etc..
Note that I use the term 'proper' because, like any other component, there are plenty of line-conditioners that simply aren't worth much and in the case of even some very popular line conditioners the sonics are actually better when you remove the line conditioner(s) from the system.
Since my line conditioners have a built-in power cable, I consider them one and the same.
Beyond that whether the ics or scs come next might best be answered by first determining which of the current ics and scs is hindering performance the most. That would determine for me which will provide better benefit.
-IMO