For as much love as the 6.5-06 gets on this site, there are a lot of people that disregard the .260 rem and .260 AI.

The PJ260 will push 140s to 2,900 fps easy.
The 260 AI will push 140s over 3,000 fps easy.
Both will be more than adequate for what you're wanting.

Also consider that both the 6.5x284 and 6.5-06 AI are going to be barrel burners to say the least.