I can not get the screens optimal resolution (1920*1080) on Ubuntu 12.04 with XFX Radeon HD 7850 card

I can not get the screens optimal resolution (1920*1080) on Ubuntu 12.04
with XFX Radeon HD 7850 card

As the title indicates I have this problem.
I recently bought a new graphics card (XFX ATI Radeon HD 7850). I have
this monitor:
Samsung S22B150
21.5 inch Widescreen LED Monitor
Gloss Black (1920 x 1080 Full HD, 5ms, VGA)
Up until now, with an AMD A4-3400 APU with Radeon HD 6410D on board
graphics card, I was able to have an 1920*1080 screen resolution, as I
have in my Windows 7 OS that I don't use that much.
I am using an DVI to VGA adaptor on the graphics card end point, only to
connect the graphics card with the monitor, since my monitor does not have
an HDMI input.
I have installed the latest driver + Catalyst Center for Ubuntu and the
biggest resolution that I can choose is the hefty 1600 x 1200 which
somewhat distorts the image, which becomes really tiring as I am using my
Ubuntu OS most of the time.
Can someone help me out with this?
PS: Any additional info that one may need should he choose to help me out
with this, will be happily supplied.