just a word of advice, no amplifier or load is exactly 2/4/8/16 ohm. when you have a 4ohm load settup, the amp could really be seeing 3.2ohm or 4.8ohm. as long as it's within the perimiter of the amps ratings and sugjested ohm loads, then it doesn't matter what ohm rate it is, it will run just fine. you just wont have an accurate power rating like what any amplifier provides for specific ohm loads.
EXAMPLE: a Subwoofer horn known as the Punisher, when using the 4ohm version of the Ciare 12.00SW subwoofer, the ohm load isn't 4ohm, it's more like 6ohm. with the 8ohm version it's more like 12ohm. it's not because of the amplifier, it's because the resistance of the speaker is not always exactly what it's rated. the 4ohm could be it's rating for it's LOWEST resistance when it could be going as high as 8 or 10ohm. all depends on the speaker...
as for 12ohm rating, the XTi4000 should do the trick, should give you atleast a good 350-400watt that way you have a tad bit of head room to work with.
Thanks for the advice. I'm aware that drivers/enclosures not only vary within rated impedance, but are dependent on frequency, as well.
The application is driving HF. 300 watts +/- 50 watts @ 12 ohm. I'd like to know the "scaling" of the various XTi amplifiers at high impedance loads, as it appears different than the Macro Tech amps I'm currently using in this application (MA's seem able to deliver higher output at higher impedances). A bit of math easily gives a ballpark answer, but I'm looking to see what the fine folks at Crown have to say about actual numbers.
I bought an XTi 4000 and have used it on one occasion, driving a pair of monitor wedges (stereo, 8 ohm/channel). The amplifier works very well for wedges. So well that I am considering a purchase of nine XTi more units, hence my question.