Unbalanced and Balanced output voltage

the true balanced compoonents most-likely will have double voltage out of XLR. in case with RCA the voltage is measured between ground and positive while in XLR the voltage is measured between positive and negative pins +2v and -2v with respect to ground.

Great question, Raul. You beat me to it. I was thinking of posting this today.
If someone can also answer the "leg" of XLR that I discussed a couple of weeks back. I have also noticed the same thing as Raul. 2V vs 4V. Is it that:
1.Some manufacturers do not prefer the "leg" approach and provide the "total" of "2V+2V" = 4V as the XLR out to the preamp
OR
2. Some manufacturers provide the figure of "2V" at each "leg" of the XLR to the preamp?
The reason I want to find is, when I switched from RCA to XLR between the preamp and amp, I got [substantial] gain. And some folks did mention that the gain "doubled". So whatever volts were going from preamp to amp - are they sent twice over + and - "legs" of the XLR?

Yes basically the negative volts from ground to ngative doubles the voltage.
With twice the voltage from the preamp you get twice the level.. out of your amp.
The amp is still limited to the rated full output.
So if the amp can produce a maximum of 250 watts. it does not matter if it is connected via RCa or XLR, the limit is still 250 watts. But with XLR, you will hit that limit sooner via the preamp volume control. just because it is sending more voltage with XLR.

Balanced is no magic bullet to increase amp power...