Your rig should be able to handle multiboxing "okey" atleast in the old context. But for pvp I think you will have a problem with lag etc.

You could go for 5xdruids. Then you have alot of different possibilities.... I box 5 druids and love it.

For mods/programs get:

"Mandatory"
Jamba
Keyclone

"optionel"
Pittbull (UI)
Macaroon (macro addon)
Questhelper

There is alot of different oppinions as to what mods/programs you need, but I started with Jamba, keyclone and questhelper and added on more mods as I went along.