Could you possibly post up a photo of the connector on that monitor? It may be a 15-pin plug with 3 pins missing... Have you any other specs on it? If it's a decent quality CRT it will give you a great picture with a scandoubler, though you will get colour banding etc. if it's not made for AGA.
An LCD TV with RGB support on its SCART connection will perform quite well with a good-quality RGB-SCART cable.
