Should i buy a new video card or upgrade my ram to 1.5gb for playing games like POP,halo1,halflife?read detail?

i am going for either video card or a upgrade of ram but not both and i don't have a PCI-E slot only AGP so i don't think many AGP cards are available now and i am not planning games like God of War so i don't think i need a large video memory only games asking for about 128MB video memory. if i upgrade to 1.5 gb of ram shld i b able to play these games? any suggestion? suggest anything other than buying a new PC or mother board.