Grasshopper provides a rich array of features, including custom greetings, call forwarding, call screening, and inbound fax. Voice mail and inbound faxes are automatically converted to email, so there are no documents to convert. Grasshopper will even read your voicemail to you. With Instant Response (included as part of the package), if you miss a call, a pre-determined text message will be sent to the caller.
Though the specific features you need will depend on the nature of your business, you should look for a small business phone system that offers:

All services are provided on a monthly or annual subscription basis. The provider doesn’t offer a free plan, but you can request a demo to explore VirtualPBX’s interface before signing up for the paid service.
Last, you'll want to take a close look at your current network monitoring tools. At its core, VoIP is simply a specific kind of network traffic, so in the end it'll be these tools that allow you to see that traffic and manage it across your network. Make sure that the tools you're using support VoIP's needs, especially around QoS, traffic analysis, and network congestion issues.