What is most important part of a system?

another issue is that DAC design is advancing fairly rapidly, esp. compared to loudspeakers

engineers seem to be focusing on noise in DACs, which can cause jitter - not just alter DR and the noise floor

many are saying that noise is being injected from circuits inside as well as outside the DAC

assuming they are at least partly correct, one is likely to have any DAC purchased be a temporary expedient, so buy accordingly

I'd also check out newly marketed DACs that advertise designs with low noise or high noise immunity

NO affiliations with any manfs., dealers, etc. - maybe a few scientists who study sound perception

So the most important thing, by far, is the power cord. It's got to be long enough to reach the outlet.

Once that's out of the way, I happen to think the room is critical. I moved last year and did not change gear at all. As terrific as my system was in my old place, and it was, I think my room is better now and my system just floors me now even more than it did before. 

After the room, I know it's popular to say it's the source that counts, but I am not really on board with that. I think the source and the speakers are of equal significance. Next comes the preamp and then the amp. 

I'm not going to get into the entire cable debate, though I do believe cables matter. And by that, I mean all cables- power cords, interconnects, speaker cable and digital cable. I am a fan of OCC cables and shielded power cords. YMMV.

It all matters that is why they call it a system . The room dictates the application of the system mostly the speakers . Smaller rooms are harder to get right with full range speakers that's why small book shelf speakers sound good in smaller rooms . If you want your cake and eat it too look into distributed bass .    

Or a bakery

Planning is the most important thing you can do. Figure your budget then look at what that money will buy you. Good vinyl, these days can be pricey and may require an external phono stage plus cables..... On a restricted budget I would think you would plan on getting efficient speakers, that way you are not left thinking you should get more watts to make it all sound terrific. That more watt philosophy does not always make sense. So high efficient speakers then sweet little tube amp, there are plenty. 

If you are on restricted by budget constrains give me a call I have plenty of gear that will test your commitment to the hobby. Good stuff however.

Jim