Don't know about vixen, but if you are using xlights as the player, almost any old piece of junk that will run xp will do ok. I use my good machine for sequencing, but I have xlights running on an old centrino laptop. It's like 8 or more years old and was not top of the line back then...
RM
Edit - I was running about 3000 channels of pixel net in 2011. LSP drove my new i7 laptop to its knees, but once the file was converted to an xseq file in xlights, no more problems, even on the old machine.