1,000 shells will take awhile to load on a single-stage, and if you are already loading 5,000 a month, adding more loading is not likely to be much fun. I agree with bmcd:
For my part, I would save my gift cards for a sale on shells unless you specifically know of a load you need but cannot find (such as a really light load).
On the other hand, since you obviously already know about buying in quantity for your 12 gauge loading, you can run up the figures using this calculator to see if it is worth it to you.
I have always used a 600 jr for loading 12, 20, & 28, and am completely satisfied, but I only shoot a total of around 400-500 shells a month.