A 300 RUM will get the job done, and well I might add. I would look at putting your $$ into your current rig. I have never seen a rifle shoot any worse after a good stock and bed job. A good barrel and trigger can close the gap even more. IMO I would rather have 1 rifle that shoots REALLY well vs. 10 that shoot like s!@t. If you re-barrel your current rig then you can choose what ever cal. floats your boat!
What part off the USA you in?