But be careful shifting things "out the door", especially if they are business critical.
We recently moved our offices and looked into replacing our aged PBX. One choice everyone mentioned was hosted VOIP PBX services.
Great if you have high-speed, reliable, internet, great if you don't mind paying again and again. For us, even though we have outsourced our Email, phone services are mission critical. If our internet connection goes down, no biggie, business goes on (albeit slightly inconvenienced), if our PHONES go down, it'll be hell and high-water combined and everything grinds to a stop.
Likewise, any business suite or accounting package better darn well be able to run in stand-a-lone mode and resync when the internet connection comes back, or it isn't coming into any mission critical situation if I have any say (which I do).
The alternative is backup redundant service, and the equipment to handle that, which, for a small office is overblown.