Are Monoblocks better than Multi-channeled amps??

most companies would put their best parts and design efforts into a monoblock pair than their stereo amplifier (which typically costs less of course). so for that reason alone the monoblocks are going to outperform the stereo amp most of the time. add the improved ventilation and the physical separation of parts that can pick up noise if located closer together and you have further gains.
better circuit pathways in a monoblock along with upgraded board materials that improve conductivity add still more benefits. in some cases monoblocks make more watts as well, so they have more headroom.
the exception is a stereo amp built to very high standards, perhaps with two
power cords coming out the back making it a dual monoblock on one chassis.
and of course not everyone has the ability to locate two amplifiers whether or not they have the extra money. there are such amps available, and you can spend an arm and a leg and even a kidney on them (FM Acoustics?).

An excellent example of this is the old Dynaco Stereo 70, a venerable 35 watt tube amp. Dynaco made something called the Mark IV, which was the exact same parts and construction except for the power transformer (which was a little smaller than the one on the Stereo 70) on a mono chassis.

The Mark IVs are obviously better amps.

This is the best example I can think of to demonstrate what we are talking about here in the OP, which is:

**All other things being equal, the monoblock amplifier will always be better.**

Less crosstalk, less IMD, lower noise, etc translates to smoother sound, better soundstage, more bass authority etc.

The other age-old argument is being able to place the mono next to the speaker letting you run short speaker cables and long interconnects vs short IC and long speaker cables. It's what I do, but there is no definitive answer to THAT question. Buy used, try it and see for yourself.

Balanced configuration is where you'll probably realize an improvement there.

Equal budget integrated amps are the best.