I 5box PVE instance on a Macbook Pro upgraded to 4GB of ram. I use a second monitor for my 4 slaves and keep my brain maxed on my laptop screen.

If you are looking for ingame macro stuff I may be able to help you out. My multiclass PVE team is about to ding 30 and I've gone through a ton of revisions on their macros and I'm pretty satisfied with the state they are in.

My biggest suggestion is keeping things simple as you can. Talent specs should be designed to keep your DPS macros simple and spamable, and keep that philosophy across your whole setup.

As for your hardware issues, try and see if you can handle 5 boxes, and then upgrade if needed.