I replaced my aging P4 system with this:
AMD Athlon II X4 @ 2.8GHz
4GB RAM
720GB hard drive
DVD/CD writer
AMD HD4200 graphics (which I replaced recently with the only-slightly-better nVidia GeForce GT 520)
Good system, although someday I will go for a real video card which means springing for a heavier power supply. Just putting that off.
I also had an old ASUS netbook which was on its last legs. I replaced it with:
AMD E-350 CPU
3GB RAM
320GB hard drive
DVD/CD burner
15.6" screen
Radeon HD 6310 graphics
I am a total cheapskate. I paid $350 for the desktop last summer, and $350 for this laptop about a month ago. Both were refurbished units (with warranty, though.)