Using a phonstage to by pass a preamp ?

Is it possible to use a phono stage direct into a power amp?
Sure, if it has a volume control built in or you have level controls on the amp.
possible yes but the volume would likely be sadly lacking. The minuscule voltage that a phonostage lifts still needs a preamp to boost it, to get an easily listenable level out from the amp.
Narrod is correct, Uru975 may or may not be. It depends on the total gain of the system. A phono stage with low gain into an amp with low gain driving inefficient speakers might not work, but there are many combinations that would.
No moreso than a CDP or any other component that outputs a line level signal.

The EAR834P comes in a version with volume control, as does the new phono
stage from PS Audio.
You can always use endler stepped attenuators at the amp end and use that as a volume control. crude but very transparent.
Sure. The Art Audio phono stages can be ordered with a volume control.