Empire: Total War is set in the 18th century a turbulent era that is the most requested by Total Wars loyal fan base and a period alive with global conflict, revolutionary fervour and technological advances. With themes such as the Industrial Revolution, America's struggle for independence, the race to control Eastern trade routes and the globalisation of war on land and sea, Empire: Total War promises to be amongst the richest and most dynamic PC RTS games of all time.
Minimum System Specs:
2.4Ghz single core processor
256MB Gfx card (DX9 compaitble)
1GB RAM (For XP, 2GB if using Vista)
I'd recommend a much higher spec than that though, there is a demo out on steam if you would like to try it.
I've got a feeling that you wont get the game for cheaper than this pre-release.