Based on my experience, I would definitely start the development of a system with the speakers. It is the speaker that mostly characterizes the sonic signature of your system. That is, electronics can change how well a speaker sounds, but they don't change the speakers' basic sonic signature. So, i would first make sure that I get a speaker that has a sonic signature I like. I would then try to optimize the electronics based on the speaker I've chosen. I don't think power cables make a huge difference. Interconnects and speaker cables, on the other hand, can make an enormous difference. The above probably suggests that the speaker is the hub of the system, something that you don't want to change that frequently because the rest of the system needs to be optimized on the speaker. For this reason, I would over-invest on it. How much depends on the size of your room. Smaller rooms afford you a smaller investment. I just bought a pair of reference 3a Decapo i for my smaller room...I invested $1200, and I believe it's hard to find much better speakers for a very small environment. Of course medium and large rooms require more expensive equipment...but even here, you can reach pretty good results with a $3K investment. If you like the midrange, for instance, Piquet modified ESL 57 is very close to the best...and they cost $3K.