Adding a Monitor to a Dell MT 545

I am replacing my Inspiron 5150 Laptop with a recently acquired  DELL 545/8707 Q8200 which came with an LG 19" monitor.

The Intel on board graphics will only drive this monitor to1360x768

I am used to working my laptop screen set at 1400x1050 with an external Dell 2005FPW 20" as an extended desktop running at 1680x1050

My original plan was to use the Dell 20" on the Desktop.

I am  struggling to find which graphic card set up to use as the majority of solutions seem to be aimed at gamers and are more expensive than I need.

I have seen descriptions of add2 cards that extend the capabilities of Intel's built in graphics but cannot find anything that will tell me if this is the way to go.

Any suggestions for a reasonably cheap solotion would be appreciated.

Regards - John