Classe DR25

I recently got a Classe Audio old model DR15 power amp
I would like to know for the right connection for the xlr input

1 pin = ground
2 pin = - negative
3 pin = + hot


1 pin = ground
2 pin = + hot
3 pin = - negative

Also would like to know if it safe to push for min 2-3ohm
loading speaker and does the dr25 sounding better than the later model
Classe twenty five?

I much preferred the Twenty Five to the DR-25 in my system. I think the old Stereophile review of the Fifteen compared to the DR-15 also applies to the 25 series.
I suggest you Google "Classe Audio DR15 manual" and look for the connections for using an XLR cable. If you cannot find the settings ( I could not), I suggest you call Classe Audio and ask them. You do not want to make a mistake on these connections.
All Classé models, including the DR-15 are:

Pin 1 = Ground
Pin 2 = Non-Inverted (+)
Pin 3 = Inverted (-)

The DR-15 will safely drive 4 ohm nominal speakers that drop to 2-3 ohms. I have driven similar loads with a DR-10, no problems.
Thanks, Gbart your information is correct!
I own a DR15, bought it brand new. I keep it turned on 24/7, never dissapoints, sounds sensational, and is as close to bulletproof as you can find. I have driven some strangely loaded speakers and the amp didn't even sweat.
I would not worry about any single pair speaker load, I would start thinking about just "enjoying the music".