got some old pc parts - which to choose? - ps1 and n64 emu

hi guys.

first of all, my intentions.
i want to play some old ps1 games, and some n64 games, but dont want to waste energy by using my q6600+amd 5850 to run some really old games.

so i dug out some old pc parts which are as follows:

amd athlon 64 3400+ socket 754, 1.5GB DDr ram, geforce 4 mx 4000/geforce 6600gt agp.

intel pentium 4 2.8GHZ HT, 768MB RAM. 2 motherboards: gigabyte ga-p35-ds3, dell optiplex gx280. ati x740xl pci-e, also have an 8800GT that i could use.

so, my question is, which do you guys think would be the better option for the emulation that i am intending to go ahead with?

also, the intended purpose is for it to also be a media and file server.

I think that the spare parts will serve you well, the computer I am running is ancient and almost all of it is spare parts. (mismatched amounts of RAM and whatnot.)