Okay, while I am not a AMX expert - Crestron is my specialty, you will need to sit down and draw up what exactly you are looking to do.
Not just "I want it to control my sprinklers", but you will need to find a specific make and model of sprinklers that are possible to be controlled. Likewise with motorized blinds, gates, doors, spas (Jandy), security (Apex), fireplace (low voltage?), hvac (Aprilaire), suveilence (lots), etc.
Every little detail must be figured out ahead of time, and really, it will take days to do it correctly. Major engineering time, then a major investment on your part for the raw materials. While I think it is great you want to do all of this yourself, the reason there are technical engineers who have jobs specializing in AMX & Crestron system design, layout, and programming, is because it isn't something you 'just do'.
As a programmer, I have heard from technicians for the last ten years who say "I've got to learn how to program Crestron." Out of about a dozen who have tried, only one ever was able to make the transition from wire-puller A/V specialist, to programmer. AMX programming requires actual programming abilities as well as graphics arts experience along with a fair amount of engineering skill.
The SINGLE biggest screw up you can have is going through a catalog and just picking 'the best'. Manufacturers (flat out) lie about the capabilities of their equipment.
IE: I recently had to program some Krell equipment. While incredibly expensive, and sounding fantastic, I saw the unit lock up several times during basic communication with Crestron. The Crestron side didn't lock up, just the Krell. It had one of those fantastic zone 2 features: When you turn off zone 1, zone 2 turns off. WTF!!! This is not the type of thing they advertise, but completely kills the value of a product.
Another example: Residential Sharp LCD & Plasma displays w/RS-232 control. You can turn the display off with RS-232, but you can't turn it back on. It simply isn't possible. You must then hook an IR emitter to the front of the display (yuck!) to turn it on. But, with IR you don't get discrete power on/off commands. Sharp has been aware of this issue for over 4 years now and they still haven't fixed it.
Oh, it isn't an issue on their commercial LCD display. Once again: WTF!!!???
If you are not intimate with home automation and AMX (or Crestron if you are open to options) and are not a programmer, then I stronly suggest you get in touch with a company that is serious about it and you can buy from. A lot of places will give away a lot of free engineering if you buy product from them. But, others will charge you less for product and put an actual dollar amount on the engineering time.
Where are you building?