Will be the Cpu holding you back, As people have it running on IGPUs by both Intel and AMD and have reviewed the performance for both. Your 6850 is alot faster than them IGPUs.
What put me off the game is not having the option or kill or knock out your enemy, only to use that long rounded object of which resembles a d*ldo... Anyway, it's time to upgrade your CPU by the looks of it son, Ol' Nessie has had her day.
It's called a sap, and it's the only thing any of the thief games had (melee). You're think too much of dishonored now. /2cents
From what I know, you've got a bow with a variety of arrows, then a 'sap', or blackjack as I think TB called it. No sword apparently, although since it's meant to be a stealth game I don't see that as a massive negative.
Currently £9.99 with bank heist DLC, must be worth a go for that price, 5% cheaper if you like them on that facebook site. i just got no money until payday ha ha LINKY
I did few missions already - very nice game. I played Thief 1 ages ago and have to say, it kept its unique climate. Good game.