Buy once and be done with it. If you get the 700 you will have to spend a lot of time / money to get it where you want it to be & it will never be as rugged as the AI rifle would be.
The AE Mark III is an excellent rifle, but you can also get some really good deals on the AE Mark II used which is also an excellent rifle.
If your budget is $4500, then assume a good used AE could be had for around $3k to $3500 depending on the deal you find and then $1000 to $1500 would get you a pretty good scope.
Now that being said, if you really want a rifle that you'll never be wanting more, you could save up a bit more and get a used AW or AX model, used they go for $4500 to $6500, you get double stacked magazines which are way easier to reload and basically you know you have the top of the line.
The other advantage in getting one of the AI rifles is you can change the caliber simply by putting on a new barrel, no advanced gunsmithing needed, just need the barrel change kit or a friend with one and you can swap to .243, .260, 6.5 Creedmore, 338 Federal, (Just about any caliber based off a 308 case size) with ease. That is a lot harder to do with a 700.
Now on the scope, there are tons of good options, but the S&B 5-25x56 or the S&B 3-20 are pretty much the top of the line scopes that will last you forever, they usually run used about $3k give or take depending on model / condition.
You might have to stretch your budget a bit, wait a bit or put some on a credit card to pay off, but if you want the best from the get go so that you don't have to buy then sell then buy again:
Good condition Used AE Mark II or AE Mark III
S&B 5-25x56 or 3-20 scope
Then add:
Atlas Bipod
Tab Gear Elite Sling
One piece AI scope mount (45 moa model is easiest to work with if using the 5-25x56 scope), 18moa, 28moa or 45moa
Low $6k budget with some good looking around should get you everything you need.
Or $8k to $9k for the same thing with an AW or AX model.
If I had to do it all over again, I'd send a note to myself from the get go to buy the best from the start rather than finding out by trial and error in ever increasing cost steps
I wound up spending a lot on good but not best stuff and could have saved myself thousands by simply getting the best from the start, true going up all the steps gives you a good education, but at a cost.
Kind of like the old saying in photography, I can save you $500 on a tripod.... Get the $1000 model first. (Vs. the $50 one then the $150 one, then the $250 one, then the $500 one, then the $1000 one).
If I had to bet my life on a setup, it would be the AW and S&B scope combo.
Just to give you an example of being rugged, when I finally got my first AW / S&B scope combo, I had it on a concrete bench at the range, while in the cleaning holder, I didn't have it securely seated and a big gust of wind pushed it just hard enough to cause it to fall off the bench 4 feet onto the concrete scope first. Picked it back up, and apart from a scratch on it, the bullets still went though the same hole at 100 yards as before.
Now a note of significant importance however is that the above suggested rigs would be rather heavy and are not well suited for positional shooting for those of weaker upper body strength, so IF your plan is to shoot in tactical matches where they all seem to want positional shooting now for some reason, then you would be better suited by getting GAP to build you a lighter more traditional stock in the 700 type design (but using a better action), also in that same vein, a Harris Bipod with the Pod-Loc may be a better choice for tactical matches as it is faster to deploy.
