Single box solution are always a compromise. If you spend enough, the compromise becomes very small... we are talking $10’sK.
I also put together my retirement system about eight or nine years ago and was fortunate to be able to upgrade again, big time, while in retirement about four years ago.
Some generalities. The investment in Streamer, DAC, Preamp and amp should be roughly equal. The speakers should be a bit more than an individual component. Buying audiophile used is preferable to consumer or low end equipment. It will sound better and last longer... certainly through retirement.
Take your time. For Streamers I recommend looking at Aurender. They have outstanding quality streamers at different price points, with exceptional sound quality and good control apps (for iPad or table to control your streamer). Used is a good option although new have good sound improvement. Dacs are more mature, but I recommend Ayre, Audio Research, Berkeley... although budget DACs, like Schiit, while not as good are excellent for the money.
Today, streaming can be and should be your best sounding source... used to be vinyl and then CD. Being retired and having basically millions of albums at your fingertips is incredible... for only $15/ month. Once your knees give out, you will be thankful.
The preamp is the soul of your system. You want a musical tube preamp... I recommend Audio Research, Conrad Johnson, or VAC. Used is great. They are built to last for decades and musical sounding... which will become much more important when able to listen for long periods of time.
I hope this is helpful. How long to retirement?