I have a Blaser R8 and one of my barrels is a .375H&H standard barrel with sights. I have had it for a few years now and it has become one of my favorites. I see Eurooptics is listing the same barrel for just under $1,500.00 USD. You can spend $3,500.00 USD on a Safari grade Selous barrel if you want but......
If your new Blaser R8 is a stand stock receiver, which it probably is since you have a 30-06, then you want to get your .375H&H in a standard weight barrel. If you get a semi weight or Safari barrel and you have a standard stock, you will need to have the barrel channel opened up to fit those weight barrels.
FYI, a standard weight barrel has a 17mm dia. muzzle, semi weight is 19mm dia. and a Safari Selous 22mm dia. Also it only takes around 30 seconds to swap out bolt heads.
When buying a new barrel ask if the magazine is included.
I have a Swarovski Z8i 1-8x24 mounted on my R8 .375H&H. I am very happy with it and think it pairs extremely well with both rifle and caliber.