That is an impressive group indeed! I can see why you would want to stay with that bullet.
Keep in mind that, generally speaking, it is preferable for your bullet to remain above the transonic velocity range (above mach 1.2) all the way to your target. The reason for that is the potential for buffeting that can upset bullet stability as the bullet passes through transonic and then to subsonic velocities. Some bullets are more tolerant to this than others. With its long, shallow boat tail, the Hornady 178g BTHP would probably be one of the more tolerant bullets. Only testing at your desired distance would tell you for sure.
With a mv of 2450, your bullet would enter the transonic range somewhere between 700 and 800 yards at sea level. A mv of 2575 would extend that by another 100 yards or so.
Though your rifle/load combination is grouping VERY well, I think it would be worthwhile to do a powder charge workup all the way to max. I would be very surprised if you don't find a higher velocity accuracy node. Here is a good, efficient method of doing a powder charge workup:
OCW Overview - Dan Newberry's OCW Load Development System
As it stands, your current accuracy load looks like it would do very well out to 700 yards or so. If you really want to go to 1000, though, I think you will want more velocity.