[groovebrother]

if you want to stay with your G4 then you should look for HD core card (pcix) and 3 accel cards (pcix). You probably will have to buy a new pro tools licence and would recommand PTHD8. The only problem will be to find tdm plugins but i guess you can find them on ebay.
But in case you'd mostly process with outboard gear, plugins might not be your priority.
But if you run pro tools hd 8 you will have to buy at least 192 i/o digidesign which you can find them on 2nd hand market between 250 & 400€ and would even better than your rme setup.



pcix cards are really cheap nowdays.


Now that been said if you want to keep on going with rme you will have to find a PTHD9 or in best cases PTHD10 licence and a mac pro 5,1 snow leopard compatible. But in that case you will need exact same core & accel cards but in pcie versions. Just a tiny bit more expensive but with some luck afforable between 200 & 300€ each. I have seen some guys selling one core + 2 accels for 300€ the hole thing. And sometimes with a PTHD10 licence included.


Good luck