ive had extensive experience with 2 of these babies for a long time under several load sand conditions.
first off, the portection circuit is just for the DC input volatge so itll go up to 18v or whatever. has nothing to do with how low u can drop the ohms on them, thats straight from MTX.
secondly, .5ohm nominal (.35ohm dcr) is bad with these. itll burp, but anything more than 5 min of straight bass will heat them up hardcore. i mean realllly quick.
1ohm nominal (.7ohm dcr) will take daily up to an extent. thing is itll get pretty warm after a while, ten itll get HOT after a while....if you keep running it afterits hot and shuts off once, then youl blow it. it took about an hour and 45min of straight bass, bass test songs, heavy rap, and tones (yes tones too) at .7ohm dcr for mine to blow. even then it shut off once of twice befor ei kept pushing it till smokage...even then it took a fairly hard *** beating to get it to that point. you can do .7ohm dcr daily but after about 45min itll get pretty warm, just be aware of the temp of the amp and if its hot enough to burn the shyt outa ur skin, give it a rest
than being said, it is still a quality amp and for 200-240 it's a SOLID *** piece of equpiment for the price. anything over 250 is still reasonable, anything over 275 i wouldnt do it...i apid well over 300 for mine a few years ago and it hought they were well worth it. if you can getem for a good price do it, they'll take some abuse and burp .5ohm nominal