PKA, I will have to pass on the OneBox. I use the Linksys SPA 9000 PBX & SPA400 VoX. I bought both for under 500. I have 6 SPA 942 Phones about $100 each.
I have a DSL + 2 Business Plans from Teliax for $150/month. With that I get 5000 minutes monthly.
I do not favor comb/multifunction devices. My server also runs my FaxServer software, from SnappyFax. $69.00. Each workstation has SnappyFax client $29.00.
The thing to remember is this. Once AC goes to SQLServer there is much less demand on the network from a wired/wireless perspective.
Backups: I ditched the tapes and dvds a long time ago!!! I backup to SOSOnline.
www.sosonlinebackup.com