The partner from Avaya can do all you want it just would use different features to accomplish it than having one box called an announcemnt box. Multiple AA's, sub menus, and annoucnements can do what you are asking.
You really are looking for a very sophisticated voicemail system, and fancy AA set up, and as Ron says you just do not know it is that until you get down to actually making a flow chart of what you are looking for in the flow of the call, and what they (caller) presses to hear what they want.
If you seriously want something which is not a sophisticated voicemail, and auto attendant set up after you draw up the flow chart I would be suprised since what you mention is an AA with options for multiple annoucements(directions, events, etc., etc.), and return to the main AA for further options.
Sounds like your looking for a no to low cost solution to provide information. If that is the case what you are looking for is what is called Music/information on hold device. You simply record all the information onto the device, and hook it up to the MOH(music on hold) input on your phone system, and put the caller on hold , and they will hear the recording which is set up to play in a looped audio file. When they are done listening they can hang up, and call back, or set the hold recall for long enough to hear the entire looped message which will make the call on hold ring again so you can answer the call once more.
With a small VM card, and ability to play MOH on transfer rather than ringing, you could have them transfer themselves to a fake ext, and fall back to VM after it times out if your message is short enough to play its entire length in that recall time. This sounds more like the budget you are looking for, even though you seem to want the features of a full blown VM with a good AA set of options, and features.
From your post, I would take a look at the IP Office with VM Pro, and see that you really do want it all. It will cost more than what you are calling simple, but what you want is more than simple, and from my experience you will want even more before you are done, and not be happy with it unless it can do everything you ask, and that is what the VMPRO is like.
If I am wrong then go with the INFO/MOH device, and use hold to communicate the info via this audio source on hold. You can have simple(low $ MOH), or you can have the impossible(IPO) the difference is length of time to implement, and price, you decide.
