Best Network Monitoring Solution for Multi-Site Deployment?

Hey guys,

I'm just looking into a piece of work which requires a Network monitoring solution across 4 sites of medium size (branch offices, but with WLAN and VoIP) and 2 Azure locations.

I'm looking into SolarWinds at the moment with distributed pollers but just wanted to see if anyone is running with a similar scenario and could impart any wisdom?

I'm thinking that if the branch offices may be fine to be polled from the Azure central location, but just trying to workout the strain on the WAN connection and/or suitability!

Thanks for any help/guidance you guys can give!