Phono Newbie

LP's will always have lower output than CD's therefore you will have to turn the volume up more.

As Viridian suggested initially, be wary of that old cartridge. If the cartridge has been sitting unused for a decade or more, it's very possible that the cartridge suspension has stiffened to the point that the it is no longer useable. Not only will the sound be bad, you risk damaging your LPs. Viridian's suggestions for a replacement are cost effective possibilities.

If you're think the cartridge is fine, you may have a some short in the connecting cables from cartridge to phono stage or phono stage to preamp that is shorting the signal and reducing the volume. Check your cables and connections carefully to ensure that they are clean, tight and don't have any stray wires touching a ground.

If you can try the phono stage in someone else's system, that will give you confidence it's not a factor (or confirm it's defective).
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I'm at a crossroads as I'm sure many here have been. I purchased the Cambridge 640P phono-pre as suggested.Whether I use my old LPs or a few new ones loaned to me by a friend, the sound has very little dimension. Also, regardless of whether I set the phono-pre to MM or MC, I have to turn the amp volume way up to get decent sound. Clearly something is wrong and I would imagine the problem lies with the turntable. So now do I invest in a new cartridge? A new turntable? Or just abandon and continue on with CD? Any thoughts?

I second the Cambridge. I have one and if not for my Sutherland, it would be my regular phono pre-amp.