I've disappeared down the rabbit warren of headphone buying a few times - its quite a journey! If you're looking for a new set it's worth trying a few out to see what suits your taste. I have ordered a couple of sets of expensive in ears from Amazon and had no trouble at all returning them (check the fine print though, some stores within Amazon can be funny). I didn't take the mick by ordering/trying loads and I did give them a clean after using them. One set in particular really lets you know if you haven't cleaned your ears out in a while - Etymotic ER4XR's - that was the day I found out how good my gag reflex is.

I have tried Sennheisers, Etymotics, Sony, and a few other brands; some cheap and some expensive. I got a pair of Shure 215's a number of years ago and they're my go-to, day to day in ears. The noise cancellation is amazing, to the point that I can be walking the dog and not hear a car on the track behind me. They loop over the top of your ear and fit snugly into the ear canal entrance so there's no chance you'll lose them if you're exercising. They have a warmer sound than a lot of headphones and for me they are lovely to listen to. I've heard the 425's are pretty good and I have a set of the 535's which to my ear sound more neutral.

You can buy the foam/rubber part separately - different sizes depending how big your lugholes are. I find the foam creates a better seal than the rubber ones. The wire can be detached from the in-ear part too so if you need a replacement wire for some reason you can get that without shelling out for a full set. I haven't tried any new ones in a few years so if you do get something different you must report back and let us know.

Good luck!