I have the same setup only with 2gigs of ram instead of one. I did successfully launch 5 clients and get them in game, however the window in focus was getting sub 20fps and the unfocused sessions were pulling about 10. This was just in trisfall glades.

Using only 3 clients it was definitely playable for me, I leveled some trials to 10 ish and even ran around undercity a bit. PVP-playable? no way.

This brings me back to the ultimate way to test if your hardware can handle X number of clients. Just go sign up some trial accounts and see how many you can log in, run around and see what its like.