Actually I think your system can still sound Okay with inexpensive speakers, but good speakers will never sound good with cheap (poorer quality) electronics.
I tried to be clear about it in my post, but appearantly was not successful. I have over $30,000 worth of electronics hooked up to $1500.00 speakers and people with much better speakers than mine exclaim about the quality of the sound I get.
My system isn't perfect, but it's not finished either. I have purposely waited till the end of my building process to worry about speakers. The next pair of speakers I buy will be much better than what I have. I really don't think I would have been able to appreciate a truly better speaker till I had my electronics in order first.
Buying speakers first prevents you from matching them to the system. The sound will change every time you replace a piece, so what sounds good today has no bearing on what will sound good when you are finished. Are you going to buy SETs, tubes or SS equipment? If you don't know what you're going to buy you are limited by your speakers. It is much easier to match one componant to your system than to match a whole system to one companant.
You will have to decide on your own which course to follow. Neither will be the perfect choice (if there really is one). I think it is much wiser and ultimately easier to do the speakers last.
The most important aspect though is enjoying the journey.