I realize you have a few of the wilder calibers set in your mind, but the good old 308 or 243 will do what you want and is far cheaper to shoot. This will allow you to get as much trigger time as possible for the buck. Remember, luck is the residue of preparation, the more trigger time, the better shot you become. A range card properly filled out will speed in shot taking and makes up for a less flat trajectory. Another consideration is barrel wear, the 6.5-284 and others like it will eat a barrel in as little as 1000 rounds. Every time you rebarrel you need to do a whole load evaluation and the new barrel may not like the loading you are accustomed to.
The rounds you have mentioned are very good ones, flat and have bullets with great BC's. They will fit in you action and do a great job for your purposes, just be sure you are prepared for the financial burden that comes along with the hotter calibers. Go to midway and check what brass and bullets will cost, as well as what more standard calibers cost. My first custom rifle
was a 308, I was able to learn how to do everything fairly cheaply. I was able to afford to go out every weekend and shoot 100 rounds without regretting it and calculating how much longer my barrel will last. That rifle belongs to a friend and is still a tack driver after almost 5000 rounds. If you're all set for what is required to be proficient with one of these rounds, I would suggest the 6.5-284. Lots of 1000 yd benchrest shooters can't be wrong.