Help with OL-Tonearm and Cartridge.

It doesn't make a sence to use hither output cartridge. If you get a hith gain phono it means you need to benefit from lower output cartridges that have better transperency and stage without loosing dynamics and presentation.
On the other hand if your phono has gain adjustment you should probably set it for 53...57dB. The gain adjustment or choosing the right gain for your cartridge is necessary to acheive the linear operation of amplification devices(not only the phono preamp).
OL arm has better phono wires and heavy counterweight that can accommodate heavier cartridges than Rega. Still there is a need for VTA which might be made by turntable manufacturers(other than Rega on wonder). Rega makes only spacers since they have their own philosophy about their arms. If you get Michell or Basis turntable you'll be able to get VTA for Rega arm. There isn't azimuth adjustment which also has to deal with the linearity of tracking.
I own Incognito RB300 modified arm and it different in better 3d stage and details due to a high quality wires, separate ground plug and heavy counterweight. But always remember that it's still REGA and not OL. It looks like REGA and it can never be adjusted to your cartridge like Graham or SME arms.

68 dB gain is very high, even for a MC phono stage. You will have no trouble driving evan a .2mv cartridge. As a matter of fact, you may experience trouble with .8mv since you will have to use the lower part of your volume control, which is usually not as linear as the middle of volume control.

Also, in general, all other things being equal, lower is better because it has a lighter coil and therefore has a lighter tip mass. If you already have a phono stage with 68dB then go with the lower output (say, <= .4mv).

The phono stage is an EAR834P Tube phono stage that I am considering using. It comes with the option of a volume control which I am leaning towards. I like the volume control because it gives me the flexibility of using it without the preamp.

Pctower, The 68dB gain is just from the MC section of this phono stage. You have to option of running this through a preamp, but I am not sure what effect that will have with a volume control on the Phono stage itself.

The Origin Live Silver 250 has a sliding infinitely adjustable VTA, unlike the Rega arms. I agree that the Rega arms sound like a nightmare to setup.

With regard to azimuth, I am not sure how you would adjust a parameter like this. If the cartridge is installed properly to a level tonearm on a level armboard, and the turntable is also level; I would think that by default the cartridge should be perpendicular to the record. If it's not then there is a possibility that your armboard may not be level. Perhaps I do not really have a grasp on azimuth.

So with a 68dB gain on just the phono preamplification can I run this directly to an amplifier with a low output MC cartridge? Whats a good range to consider?

Thanks

Yes you can put it straight into the amp, which is a great idea if your tt is your only source, or if you don't mind swapping interconnects from time to time.

If you are going to put it into the preamp first, you will want to set the volume control on the EAR all the way up. Of course, set your preamp volume very low and increase it until you find your preferred listening volume. You will want to adjust the phono stage volume downward a bit only if the the 68dB is putting the preamp volume control at preferred listening volume too low, so as to be on a non-linear portion of the volume control. (in such a position, it is more difficult to fine tune your desired listening volume.) The reason you want to put the phono stage as high as possible is that the volume control is really just an attenuator, meaning that the phono stage amplifies the signal by 68dB and then the volume control chops it back down. Since every event of amplification adds noise, and attenuation occurs more at the higher end of the dynamic range, the process of amplify/attenuate/amplify will unnecessarily decrease your signal to noise ratio.

Enjoy the music!