Erm depends are you a gamer or jsut a normal user.
these are the options i go if i was gonna spend:
PNY GeForce 4 MX 400/440 64Mb or 128Mb for bouts £90
Novatech has a GeForce 4 for bout £45 64Mb (i think)
or if your a gammer
get the new Radion :D 9700 its pricy bouts 300squids!