The use of a Sonos Bridge is to extend your wireless network to other Sonos devices, which means that you only need it if the Wi-Fi is poor, but it is also not needed if you connect the PLAY:1 via LAN.

This depends on your Wi-Fi coverage/quality. If in doubt, just try it with the Play:1. A Bridge/Boost can always be added later. You can find more information here http://www.sonos.com/de-ch...

I would try it once without. As long as your Wifi runs "stably", there should be no problems. Bridge is not absolutely necessary. Play 1 can be used without a bridge in your own Wifi. If there are interruptions, I would try changing the channel in the router. It depends on which channels your neighbours are using. This has helped me. The freeware tool inSSIDer helps you to find "your" free channel in the wifi. If that doesn't help, then get the Boost :-)