Another Headphone option the semi close Fostex TH900. They are far less picky than the HD800 with amplification. They have really good bass and well extended treble- slight spike for younger people but if you’re 40 years plus no issues. This should work well with organ music. They come up on the second hand market usually around $900. They also like the HD800 (Though not as large) have a wide sound stage for a semi closed headphone.
i have had both headphones and would suggest the TH900 were more enjoyable across a wider variety of amps including portable and the HD800 a better tec