you probably need to rewire your entire homes telephone wiring, as most residential phone wiring is run in a loop, or from jack to jack, while if you are thinking about using a PBX or phone system you would need to have home runs for each extension...
so you would need a box of CAT 3 or CAT 5 wire...
you would also need a 66 block or 110 block to terminate the wiring..
you would need some cross connect wiring..
you would need to purchase a phone system with an IVR...
assuming that you do not want to have wired proprietary phones all throughout your home you would need a system that you could connect a regular analog phone up to..
seriously for most purposes a phone system for residential use is overkill... the cost is far greater then any possible benefit that you might get... besides how would any of your callers know where in your home you were to call the family room or basement extensions?
then there is the fact that you probably are thinking that you will be able to make multiple calls at the same time while someone is on the phone - which would be wrong unless you got multiple phone lines....
a much better option would be to just get 2 lines and a 2 line phone...
however there are some options... there are some phones such as the AT&T 10x0 series of phones (1040, 1070, 1080) that have many features of a phone system... the 1080 is supposed to have an IVR built into it... this method would not require you to have to rewire all of your phone jacks... but it would not provide all of the options that a phone system could, such as a door phone... (although you could always pick up something from viking and connect it to one of the additional lines on the phone - as long as you do not have 4 phone lines) but for the phone system features to work, all of your phones would have to be compatible with each other... which rules out cordless phones (at least if you want them to interact with the additional features that these phones provide)