Magnepan 3.6 or 3.7 - The smart choice?

Hypothetical: If offered in excellent-mint shape used MG 3.6's for $2000 or MG 3.7's for the price of $4000 - yes $4000 not $5500-5900 - what would you do, which is the smart choice? (if the 3.7's were over $5k i wouldn't ask this.)