The Action PAR-30s are not dimmable.  I was working on a dimmer adapter circuit for them but then I had some safety/reliability issues with them and abandoned the project.

 

The Action MR-16s are dimmable (sort of).  While it doesn't say on the newer ones (it used to be printed on the older ones), these are AC 12V... not DC.  They can be wired 10 in series for AC controller use or can be put on a DC supply of 13.8V (I've done both with success).  When going the DC route you will need to set your board max intensity to 25% to achieve halfway reasonable looking fades (but a 33% command is still about 50% in real life).  Note: 25% max intensity is still about 98% brightness... so it's not like you are making the bulb too dim to be useful.

 

It has been suggested to me that the Action MR-16s may be able to achieve more linear fades with a series resistor.  While I haven't tried this (yet), it does make sense as the LED property which aggrivates this non-linearity phenomenon is the fact that their apparent resistance changes as the current changes.  A series resistor will pad this effect because the controller will essentially see the sum of the two resistances instead of just the wildly varying LED one.  Since the one resistor is constant, the percentage of overall resistance change will be less than that of the LED on its own.  However, (in theory anyway) to achieve any useful linearity might require a high enough resistance that the voltage drop across the resistor is a problem (higher wattage resistor and higher supply voltage become a problem).  Since I have nearly $1k in these floods (and have some set up in the office for testing Aurora), I will be experimenting with this at some point in the next month or two.

 

I have not tried PAR20 bulbs of any kind.