Are Monoblocks better than Multi-channeled amps??

In general, monoblocks are better than multi-channel amps, mainly for 2 reasons:

1) Separate power supplies provide more instantaneous current to the output stage.

2) Because the L/R circuitry is housed in separate chassis, there is no interaction between the two (better separation and soundstaging)

Whether the added cost is worth it depends on your priorities, wallet and space.

bondmap,
I would agree a top level and high standard built stereo chassis would likely out perform a modest design and built monoblock amplifier.
However when companies offer both choices or go 'all out'their monoblock version is the upper tier amplifier with rare exceptions Same as when a product can be silver or copper(cables,amp wiring,transformer windings etc.), the silver version within a line is the upper level version.
Regards,

Monoblocks take up too much space for my purposes, otherwise all good. I think another good idea is to buy well designed stereo amps that can be converted to mono when you have the budget (and/or space) to get another one. The conversion is often easy (or ready to go in the design) and you're jammin' as soon as "amp 2" arrives. If I did this with my current Jolida 502p I'd have 2 monos making 120 watts each for under $2500 total for both sides...and be able to shut off the winter heat in my listening room.

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.