Hi @EchoMaster
Welcome to the Sonos Community! And thank you for considering Sonos.
A Beam can easily serve as both a streaming speaker and a TV soundbar, but if the combined area is large enough that you might want to have one person watching TV while another listens to music in the kitchen - or, if you just want the music in the kitchen to be a little more local, adding a Era 100 would certainly do that for you. I can’t imagine you not being happy with the improvement in sound quality over a first-gen Echo with either speaker.
In terms of future-proofing, Era 100 is one of our newest speakers, and we’re still releasing the occasional update for devices we first produced 15 years ago - I don’t think you have anything to worry about on that front! Beam (Gen 2) is also pretty recent.
For second-hand items, I recommend using one of our official eBay stores - although the speakers there are second-hand, they are refurbished and come with full warranties. You can find them here:
As you already have a speaker in each location, you might want to just start with replacing the one you like the least, first. Or, another way to look at it is that if you buy an Era 100 first, you should then be happy enough with the sound quality to then feel better about splashing out a bit more later on for the Beam. In terms of value, this would depend on what you do the most, I guess - cook with music, or watch TV/Movies. I think buying a speaker to address whichever you do the most will result in the best value, as it’s pretty subjective.
As you have mentioned getting second Era at a later date, I’ll mention that you would then have the option of adding the two Eras as surround speakers for a Beam. Please be aware, however, that these would then be unable to operate independently from the Beam unless reconfigured (losing surround). Sonos is of course modular, so you could add a third Era and hold-off on surround sound until then, or forgo surround entirely.
Both versions of Beam use HDMI, but come supplied with an optical adaptor - they should therefore work both with your current TV and future TV , so no worries there. Note that some older TVs will not pass surround sound audio to external audio devices - you’d need to contact LG or find your TV manual to know for sure (stereo audio would work, however).
Basically, as long as you are happy with the result, there are no wrong answers for how to start your Sonos system. If you buy from our eBay stores, you will have a 30 day money-back-guarantee period, versus a 45 day period (in the US) if buying from our website - if you are not entirely happy with your purchase, send it back and we’ll refund you (and pay for shipping too).
I hope this helps - if you have more questions, please don’t hesitate.
"Common sense is the collection of prejudices acquired by age eighteen." - Albert Einstein