Well to be honest with you, I've invested a lot in Stereo systems ( more than $90k ) as my I'm an audio freak, more like an obsessed audiophile.
A $4000 speakers paired to a $2000 AV receiver will sound good, actually great for the majority of people in 2 channels or multichannel mode.
However you should listen to a pure dual monoblock amplifier paired to a nice set of stereo speakers . The difference is like day and nights.
DSP in receivers affects the sound quality a lot. The electrical measurements also show the equivalence (SNR, THD, Crosstalk, FR, etc). Even if you have a bypass, it's never gonna sound the same.
With surround, you're budget is limited, The most expensive around is probably a $6500 ( Denon 5xxx ). A pure power amplifier price ( depending on Class ) can start from $10k up to $200k and there's a reason for that.
There's still nothing like good separates, or even vintage. Ask any audiophile ot check audiokarma, avs and headfi forums
My current setup however is iMac -> Toslink > Benchmark DAC1 > Jh16's Pro custom IEM and FLAC ( mainly 44.1KHz/16bits and some 48 and 96KHz although you can rarely tell the difference between sampling rates ) Sound quality makes me forget about any AV receiver or low budget stereo system.
PS: I think we're hijacking this thread. Any objection
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