From what I've seen a 25-06AI should push a 115gr bullet somewhere around 3300fps maybe a little more and most of the 6.5-284's I know of with normal length barrels will run the 140's around 3000fps.
Setting JBM at 29.92 Baro 0 elevation and 70 F temp at a 1000 yards the 115 Berger gets to 1000 yards 1552fps with 615 ft lbs of energy and the 140 Berger gets there with 1681fps and 878 ft lbs of energy, the 115 is flatter but gives up a bit of windage to the 140. I wouldn't shoot a deer at a 1000 yards with either at that elevation, to me it looks like the 6.5 gains you maybe 30-50 yards unless you push it substantially more but from what I've seen that about where they run. A deer or varmint won't see a difference, after looking at those numbers I'm very glad I hunt at 6000-9000ft elevation!!!!!
"Pain is weakness leaving your body"