I see your confusion, I was in your position a little over a year ago, so I'll give you some general clarification... Shooting "benchrest" doesn't just mean shooting off a bench - BenchRest (or "BR", as you'll more commonly see around here) implies shooting targets using a highly customized rifle that is generally designed to be shot off of "supports" vs. holding it in your hands. These supports include a "pedestal" adjustable for height (and possibly windage) that supports the front of the rifle (where a bipod would be), whilst the rear is supported by a leathery or synthetic sand/bead-filled pouch (colloquially known as "bunny ears" because of the shape). The goal here is to:
1. Build a BR rifle using extremely tight tolerances and a scope that is very stable
2. Experiment with different casings, powders, bullets and primers to find out which combinations and hand-loading techniques work best with the rifle.
3. Learn to read wind so that all your rounds go into the same spot at the distance you shoot at... There is short range BR (100-200yds) and long range (1000yds).
There are also different categories of BR competitions with different weight restrictions, since BR rifles are relatively very heavy: it's not unusual for it to weigh 20 lbs or more (Google "BR railgun"), even though the calibers used aren't very big (again, relatively speaking). This is not a rifle you can sling up and go to the bush with or take to war... Trigger control is basically the only "physical" marksmanship involved here - you won't be shooting between heartbeats or something, since your finger is the part of your body applying the most pressure on the firearm. The point is to achieve accuracy by means of reading the external conditions (wind, mirage, etc.), the conditions going on in the firearm (heat, fouling, wear, etc.) as well as the cartridge (powder burn rate uniformity, case wall uniformity/malleability, bullet land engagement, etc.) and firearm preparation to ensure consistency throughout. No small chore, I'm sure the BR shooters here can chime in... But it ain't really my cup of tea.
Some categories award the person that has the tightest group, others with the number of rounds closest to bullseye.
So just because you're shooting off of a bench doesn't mean you're shooting BR!
In "tactical" shooting (or sniper matches, whatever), you referred to the position correctly: "prone". People will all understand what you're talking about. But when you sight in your new scope, you're doing it "off the bench", you're not shooting BR.
Going prone is also done in service rifle shooting (generally with the aid of a sling), F/TR-class, CIS/UIT 300m, Palma, Bisley, the list is exhaustive. This is where you need to physically control and adjust your point of aim, so the accuracy acheived is generally less than BR, depending on the style of shooting. Prone can mean using a bipod alone, a bipod with a rear bag supporting the stock, or with only your elbows on the ground with the rifle being held up, usually with the help of a sling to keep the jitter down.
As for your selection of a rifle, I'd recommend a heavy-barrelled Savage model 10 with an accu-trigger and accu-stock in .308 Win. Should be versatile enough for tactical shooting and hunting, even though somewhat heavy for the latter, so get a sling to haul it around. Top it off with a Leupold Mark 4 or Nightforce NSX (depending on budget & weight), and I'd say you're set. If you want real versatility, get a quick detach mount so you can switch between a tactical scope and a hunting scope. Don't cheap out on optics.
Enjoy!
