First, I added a normal CDP, then added a component speakers, then decided to add an amp and a sub.

From there onwards it was pretty much jumble sale! Hahahaha...

But I think if this is the case, then

1st - HU - This is the source. If you have a good HU, you wont need to worry about upgrading, at least can tahan a few years la... Unless budget means susah sikit

2nd - Amp - Amp not cheap... Hahaha... For me now, no return. Die die also Class A. Get a good amp and you can live with it for a few years.

3rd - Components - Too many good stuff outside and one of the most upgraded parts in ICE...

4th - Cabling - The one that yields the least difference in most folks ear and can be very expensive...

5th - Wong Fei Hung close shop...Run active? Can... But costly...

But looking at everything, it co-relates. If you upgrade one thing, you might need to upgrade another.. Wahlaio!