If I understand your requirement correctly, you only use this for playback. If you want rock-solid, luckily for you Echo are Linux-friendly and your Indigo will be supported by any current Linux installation. This will keep your hardware working perfectly indefinitely. Just render your tracks to audio files, and play them with e.g. VLC. There’s really no reason to use a DAW for playback during live performances.
If you really want to trust your live performances to Windows or Mac OS, then IMHO RME is the way to go, if only for the quality of their drivers. RME may seem expensive, but if I add up the cost of all the other cards I’ve used, and then add the time I’ve wasted trying to get them to actually work properly, I would have saved money if I’d gone with RME in the first place.
My second choice would be MOTU – certainly if you’re using Apple – but until recently they have been somewhat less supportive of Windows (that’s just my personal experience). As you already have a MOTU, the bad news is that MOTU are very hostile towards Linux, so that limits your options.
You could always try Steinberg hardware, but I’m sure you will have gathered from other sources that people have lost all confidence in the company maintaining driver/firmware/software support.
This neatly brings me back to my opening observation that your Echo card is well supported under Linux, and that won’t change … if I were you, I’d sell the MOTU and buy 3 or 4 old laptops on eBay, install Linux on them and either use the Indigo or choose a USB RME card.