Ring Central is a good choice for a virtual phone service for businesses. For what your looking for (1000min & $9 a month) they may not be suitable, but I recommend them due to their service and performance. From a business-minded point of view, I recommend coughing up the extra cash, for something that will provide better service.
Like eLiTeGuRu stated, SkypeIn and SkypeOut is an excellent choice if your looking for something simple, they also have very low rates for calls around the world.
I'm currently a Google Voice user and I must admit that although I love their service, I have submitted a request that they provide access for business in the near future. If they do create a similar service for business use that allow for multiple phone numbers, I believe they can be the top choice for what you may be looking for.
They should be able to provide you with a virtual phone number (or more if you need them) with an area code of your choice. Though, your budget is pretty low for 1000 minutes, so you may need to expect to pay more unless you commit to a longer contract or pay more upfront.