Definitely a matter of preference. But keep in mind that Pastel female, if bought as a hatchling, will take a couple years to be within breeding range.

Any double co-dom male would be good, depending on what you like, most are below the $1000 range. Pastaves, Pewters, Bee's, Blasts, etc etc. will all reproduce themselves when bred to your normal.

To make it a bit more interesting, what I would do is buy your double co-dom male for your current normal female (when shes at least 1300 grams) and then buy a young double co-dom female and grow her up. Quadruple co-dom in a couple of years (depending on what you get).