Light & accurate huh?
I would suggest you take a very close look at the CZ-527.
It is an exceptionally accurate light rifle right out of the box.
I have one in .223, and my hunting bud has two, one in .223 and one in .204.
All three are capable on one-hole groups at 100 yards.
http://cz-usa.com/products/view/cz-527-american/ http://cz-usa.com/products/view/cz-527-varmint/ As for scopes?
A quality 3x-9x or 4x-12x variable is plenty enough for PD's at 300 yards.
If you go with the 12x, be sure and get one with adjustable parallax or AO.
I would look at Leupold or Pentax.
Forget the cheap Chinese scopes like BSA, Leapers, etc. Any cost savings up front can quickly be lost in ammo expense and shooting confidence if you get one that doesn't track right or hold zero.
As for caliber?
Either is a good choice.
The .223 is easier to find ammo for, and has a better selection of bullets if you plan to reload.
The .204 shoots a little flatter, but is more susceptible to the wind.
rc