My thought is that updating the LP12 would be more cost effective. I think you would have to spend more than the updating cost in order to get the same level of performance from a new table. Although it is true that the LP12 is an old table, Linn keep it up to current spec if you take the upgrade mods they provide over time.
I believe that Linn are finalizing a major upgrade to the base and armboard. I think it's called the Keel, but I'm not sure of the details. Somebody else may be able to provide more information. If that is the case, you might want to hang on a bit to see what its about and what it might cost.