Welcome.
I’ve tested and keep around lower cost reference setups for this very purpose [see that entire thread]. Not everyone can afford the pricey stuff and many people want to test before going hog wild. A modest system will never match a high end system, but they do sound very good. The law of diminishing returns is real – you pay a lot more for the improvements.
I currently run my HD 600 with the iFi ZenDAC (<$200). It has an internal amplifier and enough warmth to offset the 600’s brightness. The 650/6XX is warmer, and may be too warm with this setup. See the link for other ideas.