Your dilemma is the classic one we all face: how do we get lots of power and velocity without getting the c-r-a-p kicked out of us by a hard recoiling rifle. The "muzzle-brake" birds will be on here soon, touting them. For a HUNTING gun, I think they are a nightmare. But to each his own. (By the way, your GUIDE and HUNTING PARTNERS will not like the muzzle brake either. They are DEAFENING to everyone around them.)
Let's talk options. First off, if you have a .30-06 you already shoot well, just go with it! With modern bullets it is awesome. It'll get the job done. Shot placement (as with ANY caliber) is really the key anyway.
Secondly, if you really just WANT a new 'toy' (.300 Win Mag? .338 Win Mag?) Then WEIGHT is your friend. A heavier rifle will kick 'softer' due to decreased recoil force and recoil velocity. Go 10 lbs on your gun and, hey, it's almost like your .30-06! Of course, carrying that weight while hunting isn't fun, but everything is a compromise.
Third, mitigate recoil with a LIMBSAVER recoil pad and a MERCURY RECOIL REDUCER in the buttstock of your rifle.
Fourth, lighter bullets kick less than heavier bullets. If you go with a BARNES TSX/TTSX or Hornady GMX or HAMMER bullets (reload only) then you can go down a bit in bullet weight and still get the penetration of a heavier 'lead' cup & core-type bullet.
I vote for the .30-06, as alcesgigas suggested. You won't be alone. You'll have a guide and perhaps even another hunter with you.
If you really want a new gun, then get yourself the one you already show an interest in (the .300 WM) and try some of the things I've mentioned to reduce the recoil.