Howdy, and welcome back, Maph
The best combination of clients to run on your 9550 + 275 system depends on how the system is run and what you want out of it. If you use it a lot, the GPU client will detract from all sorts of things by dominating the GPU and slowing down display updates on games. Some people stop the folding client when gaming and start it back again after stopping gaming. If you're running one SMP client at the same time as the GPU client, you'll have 2 cores left which should be sufficient for most uses, but if you want to run 2 SMP clients, then you may have interference with the GPU client's output, slowing it down.
It also depends on which OS you're using. And other things too, possibly. Give us more information about your setup and its uses, and we can offer better advice.
(BTW, there's a Back Porch thread
of the same name as this one started by AmishRakeFight
about his return, though I don't recall having seen him around since then.)