Eric
I replaced one on my backhoe recently. I went from a 12 gpm to a 20gpm. There are advantages and disadvantages to adding a larger one. Advantages being-- everything is faster if you run it at your normal operating rpm, and you can usually run at a slower rpm . On the other hand, many of my hoe movements are more jerky and not as smooth as they were with the smaller pump. Operating pressures will be higher than before due to the increased flow and relief valves and cushion valves that may have been hardly used before maybe used constantly now. The only reason I went to a larger pump was because my old pump was worn out. A new factory was $958 and an after market was $600. The after market only came in a 20 gpm and rather than spend the extra, well you know. I only use the hoe for my property, but if I was using it commercially, I'd of bought the factory one.
If you want my 2 cents, I wouldn't get a bigger one. The tractor was engineered for that size (horsepower, gear ratio on pump) and might not behave like you want .
Gollum