I would say Both extremes first:
Speakers and transport.
Electronics do a good job most of them as long as you pair them correctly (an 8 watt SET and 86 db efficient speakers is a bad pair). Yes the preamp is very important, or the inexistance of a preamp...biamping also jumps you far ahead.
Most of the money should go for speakers and transport, but you have to shop around, of course you can find very expensive bad products, price is not an insurance for quality....(general rule no pun intended).