what are everyone's thoughts on the er4sr vs er4s/pt? i'm in a dilemma since the er4s/pts are quite cheap nowadays brand new, around ~200. is it worth the price difference since the sr's are never below $350.
I'm a little late on this, but here's my perspective. I've had ER-4S since 2002 and it became and stayed my "reference sound" nearly all that time, while others came and went. That's a decade and a half now! So IMO it's really, really good. If you fundamentally like the Ety sound, you won't go wrong with it even though it's not the newest.
I also have an ER4-SR now, and I think it is even better. I'd describe it as literally an improved ER-4S, and I do prefer it. Looking upward in this thread, not everyone agrees with that, and some like the ER-4S a little more, at least for some purposes.
If cost is an object, I'd say go with the ER-4S. If it's not, I'd recommend the ER4-SR. Both are just great.
Both, IMO, "need an amp" and will pretty vividly reflect the capabilities of the upstream electronics. Yes the ER4-SR is easier to drive in the sense that you can get more volume out of it from a laptop or phone audio jack, but I don't find it to sound particularly good this way. (FWIW I find this to be true even of the hf3 and hf5, which "should" be silly easy to drive but which improve shockingly with an amp (do try it, if you have one of these).)
FWIW by this point I have three ER-4Ss, of varying age. All are still going strong. I've replaced the cable on one with an aftermarket cable that's a little shorter, for less awkward portable use. My SR generally stays at home, and the recabled 4S goes on my portable DAP. Something like that might work for you also if you start with the 4S and later decide to add an SR.