sflr,
I have had two 6415's. The last one that I traded for was right at $47,000 with a 640 self-leveling loader. I'm not sure if your price included a loader. I would hope it did. I just went to Deere's website and the base price for the 6415 mfwd with two remotes, which would be more than adequate for your operation, is $54,000. That's list price. I could get that tractor for $41,580. I'm not sure what all you put on one but I put virtually every option available on the configurate and couldn't get to $67,000 on a 6415.
As far as hydraulics you won't notice it much if all you are running is your 567. I would check the requirements on the 567 baler though. It requires alot of force to keep the doors closed on the 567 but I think 18 gpm would be enough.
Basically your hydraulic flow is going to determine how fast you do things. If you're doing alot of loader work your recycle times will be significantly faster with the 25 compared to 18 gpm. Alot of machinery is hydraulic dependent. Meaning you have to have a minimum gpm flow to run that piece of equipment. Our planter, for example, requires 35 gpm.
For your operation either tractor is going to serve you well for years to come. Pick whichever one suits you best and you can make the best deal on.