Thanks for the reply. Yes, these won't be living room headphones. The Senns lasted about a year. I appreciate the other suggestions.
As for the Leckington, no changes. Using it just the way Nick sent it to me. I just got the 400is a few minutes ago, so I won't be able to try the Leckington until later this evening. But I'll let you know!
Interesting, though, about the 400is....they come to life with an amp! When I got them I plugged them straight into my Nexus 6 - not enough gain, not much bass, not much of anything. So I tried them direct into my XPS. Again, not a whole lot of volume, hardly any bass. But then I remembered I had an 6-year old NuForce DAC, which cost maybe $30....tried it with the XPS and the 400is - and they opened right up! They sound phenomenal, with just that tiny little push.
So I'm really excited to try them with the Leckington!
Agreed with @DavidA, I don't think the 400i will last too long when subjected to your described use, especially if the 650s broke within a year - they have the plasticky feel, but are quite durable nonetheless. But who knows, eh?
Do keep us updated, and welcome to the bunch!