Buy yourself a used action, buy a quality barrel, and stock of your choice. Have a good gunsmith build you a custom rifle
. If your going to take it to a smith anyway and have him accurize it then might as well go all the way and build a completely custom gun.
Shilen, Hart, Douglass, Lilja, Krieger, PacNor are just a few examples of high quality barrel makers. You can usually find a used gun anywhere for a lot less than you plan to pay for the sps. Sell the stock on ebay and regain a few bucks.
If your looking at launching anything higher than say 180 ro so then use the 300 win mag, if you looking at shooting anyting below that weight then I would suggest looking at the wsm series of cases. More efficient, and a shorter case could mean a lighter rifle depending on action length chosen.
The 300 win mag is a good choice of claiber for long range hunting, nothing wrong with it either.