My Sennheiser HD 555 ear pads have worn out. But I just realised my 555 is nearly 20 yrs old.
What’s a good up/side-grade from the Sennheiser HD 555 around 10k?
Do I go with the similar 599 SE or are there better options? My preference is for the Sennheiser sound.
Also have a look at HD 560s. This has better imaging and tighter and more balanced tunning than 599/599 se.
The 599 has elevated mid-high bass along with more forward upper mids into the treble. It plateaus at 1k-2k so it trades the quality of the mids for a more dynamic V-shaped sound.
Although the 560s has terrible noise isolation, but that may be attributed to the open-back design.
I’ve heard nothing but good things about FiiO FT-1s if you extend your budget slightly more or find an used one…
This is a closed back headphone so the sound stage delivered by these wil be inferior to the open back design of Sennheiser 560s/599/599se/555.
OP has been driving open backs for past 20 years so they are accustomed to the wide sound stage and now shifting to close backs will be a major change for him
On plus point you will get way better sound insulation.
Though if ft-1 pro offers the same tunning as ft-1 then it can be considered as it’s a open back design.
You still get replacement ear-pads -
I’ve bought these replacements and also from another brand called Crysendo a couple times. Despite the cost, the inner stitching tears up in less than a year. And i take good care of my gear.
We don’t really have many options though. So it’s better to go for the cheapest option. 1.8k for this stuff is just too much.
Unfortunately old models don’t have much quality options unless you go custom, which will still be costly. The OEM sells aftermarket pads for some models so Senn India can be asked. Dekoni and Brainwavz makes decent pads but not sure if they stock this. According to this, other model pads may fit but ymmv. Perhaps OP can replace the earpads, sell it and get new headphones.
Rs 1.8k for two pieces of foam 
I have a HD 598 SE nearly 8 yrs old, the ear pads and headband have worn off and I am looking to replace them, but at these prices better to buy another headphone for 10k than replace the pads and headband for 4k
Also keep in mind you probably wouldn’t like how any replacement sounds for the first few hundred hours. Twenty years is basically a life spent with ever-sweetening sound, anything new would a drastic departure.
Back when I cared about these things, I wouldn’t put a new pair to my ears until I had put two weeks of audio through it inside a closet.