IF I wanted a rifle for mostly deer, 500 and under with an occasional elk, and I didn't reload I'd probably go with a 30-06 or .308. Honestly for deer out to 500 a magnum isn't required, any of the .308 or 30-06 basic cartridges will work well and handle an occasional elk at sane distances. They'll also be easier on the shoulder and wallet. Flat shooting magnums work well for western spot and stalk, especially when there's wind involved, but how much of those conditions exist in TN?
IF I HAD to have a magnum "something" to keep up with the Jones's, I'd probably get a 300WSM. IF I wanted a long action, I'd probably stick with 300Win Mag cause ammo isn't horribly expensive and can be found. There's a few smart guys around that swear that the 7mm Rem Mag is about as versatile cartridge as there is.
Unsure of what the OPs friends disposable income is, but for most folks not reloading and owning a 28 or 30 Nosler or 300 RUM is a recipe for not shooting much. They all cost serious $$ for factory ammo.