US4k to 4.5k will buy a pretty good mid range "proper stereo" well beyond the usual Bestbuy dross, but not a really high end system.
Something like a Cambridge Audio CXA80 ($1000 on Amazon) plus a CXN network player ($1100) and a pair of Monitor Audio S10 floorstanders ($1250). Add $500 for decent speaker cables and interconnects and that comes out at just under $4k.
Then you add, say, a Yamaha 850 7.2 receiver ($680) with all the latest HDMI, HDCP, HDR, 4k passthrough, DTS:x and Atmos capabilities (which most "boutique" AV receivers don't have, sadly), and that's $4500 well spent (assuming the Cambridge and MA kit works well together, of course). A centre speaker, a sub or two, surround speakers, etc. can be added later as the OP's spending money allows. Talk to retailers and wave Ben Franklin's at them and a centre speaker, for example, might get thrown in for free.