DiZiTech

You could either add another amp and use one of the audio outputs from the EA3 to feed that amp or you could add a triad one.  

'Bigger' sound?
Do you mean:
-The volume isn't enough?
-The volume is fine but it sounds as if it's low on bass
If the volume isn't enough, I suspect 4 speakers are connected to 2 outputs, and you may want to use 2 outputs
If the bass isn't enough, depending on the exact amp you have, it likely has a sub-woofer out, and that's what you'll want to do.
 
Both the EA3 and most Episode matrix amp have fairly detailed equalizers, and you could use those to try and ;tweak; things without hardware. The EA would require Composer (HE I believe will do) - the episode amp could be done via it's web interface.

I don’t use KNX, but if I understand you correctly, this problem has a solution.
1. When Relay 1 is closed, set your experience button state to on
2. When Relay 1 is open, set the experience button state to off
3. When the experience button is selected (not set to on), toggle the Relay 1 state.
 
This approach will allow you to track the state with your experience button, operate the relay with your experience button, and still operate the relay with any other control method you already have set up. There will not be an infinite loop.
I hope this helps.

Yes - you won't be able to get OSD out of it (navigator display on TV) but that doesn't matter for your needs.  The project can run 3.2.3 with an HC800 in it.

Adding an old HC-800 into the project will give you another 4 zones.  That's probably the cheapest way.
 

need a little more info on what your trying to do, i dont understand your question 

If I'm understanding correctly - you want the AC off if a door has been opened for more than five minutes, and when all doors are shut, turn back on the AC. Now I don't have any way of testing this, and I don't like "when variable changes," so give this code a try and let me know if it works. Might need some additional tweaking.
When DoorA opens
  do DoorOpenMacro                    !I like macros - helps keep code in one place
When DoorA closes
  do DoorCloseMacro
etc.
 
---
DoorOpenMacro
DoorVar += 1
if DoorVar = 1                              !if more than one we've already done this
  ACVar = status of AC                !need to know status of AC - it could be off - like in winter (if you need help with this code let me know)
  if ACVar = on
    Start 5MinuteTimer
 
---
DoorCloseMacro
DoorVar -= 1
if DoorVar = 0
  Stop 5MinuteTimer                   !this line of code is actually not necessary - can wait till timer expires
  if ACVar = off
    start AC
---
When 5MinuteTimer expires
  if DoorVar > 0                          !is door still open?
    stop AC
    ACVar = off

When Door A opens
    If Timer is not running
        Restart Timer
When Door A Closes
    if door a is closed
        if door b is closed
            if door c is closed
                Stop Timer
When Door B opens
    If Timer is not running
        Restart Timer
When Door B Closes
    if door a is closed
        if door b is closed
            if door c is closed
                Stop Timer
When Door C opens
    If Timer is not running
        Restart Timer
When Door C Closes
    if door a is closed
        if door b is closed
            if door c is closed
                Stop Timer
When Timer Expires
 Set AC = Off

pathsetter driver would also work for this. you could also use any digital amp driver and fake it as well.

Driver is called "Universal Adapter" under Control4 manufacture 

Nope, though worst case, its essentially a video switch driver with one in one out, and 'can convert signals' option checked - then I just add all in and output types...

Just need a driver for it - should be one in the database already - that allows digi in and stereo out to let the system know there's something making that change