I wonder if it wouldn't be more worthwhile to have your iMac stripped down by a repair shop and the thermal paste checked/replaced with the best stuff, the whole thing cleaned out if that is an issue, etc. instead of buying a now dead-ended machine costing at least 6k that will require further investment to compete with an i9?
Heck, you could probably get a noise proofed computer cabinet for the little offender and a swanky external screen for way, way less.