For your choices;
The MTX I heard, will heat up really quick if modded since it wasn't meant to do 1 ohm anyways. The protection is there for a reason. Modded 81000d's are just plain 81000d's with the low imp protect removed so it doesn't go into protect. Doesn't mean it's stable at 1 ohm though.
The SS PCA2kd will do 3k at .5 ohm if you have the electrical to back it up. Post #3:
http://www.icixsound.com/vb/showthread.php?t=35456&highlight=pca2000d
The Brutus, although hated by many followers here, will do rated power at 14.4. The 07's and 08's were updated to run a bit more efficiently. Calculations at 12.5 volts shows a bit over 1700 watts at 1ohm.