What graphics card should I choose for playing Civilization 5 on a 42 screen?

[xAxis]

I haven't bought/upgraded desktop pc since 2007, and haven't been seriously following trends since. So, this morning, after all night researching about processors (it was very difficult to classify them by quality, not like old Pentium 1-4 days. In fact, I couldn't even determine what generation after P4 are the latest core I processors) I bought core I7 290 @ 2.67 GHz mounted on Asus P6t SE Mobo with 4 GB ram (ddr3).
The graphics card is miserable, but the price was good overall. Now I want to buy a graphics card.
I am not much of a gamer but would like to be able to play my favourite: Civilization 5.
I also intend to buy big 42inch screen, and am not sure if that is important for the choice of graphics card. I'd like to use High definition so as to enjoy Civ5 and maybe few racer games.
I found this Radeon HD 5750 with 1GB memory for £60, which is in my price range.
What would you advice me? Are there any other good models in range 50-80£, which is $80-120 (I guess) And are there any differences between 42" and common PC monitors.
Thanks for any advice.

 

[xAxis]

When I say differences I mean , for instance, if above mentioned Radeon HD 5750 gives stunning resolution for common pc monitor, on bigger monitor (42") I guess to look equally stunning would have to have much more pixels (bigger resolution). So is it then simply covered by more Vram (say 2Gb), or has to have some extra fiture, like hdmi, which I know nothing about.