I don't know about the 4550 but the 6570 is said not to be good for gaming, see:
Personnaly I went for a 6850. when I'm not gaming I set max fan speed manually at 28% to keep it silent.
All the GeForce 4xx/5xx GPUs support every HDMI 1.4a 3D display, so do Radeon HD 5xxx/6xxx discrete GPUs (yes, 5xxx too), as well as A6/A8 Series Fusion APUs (Radeon HD 6530D/6550D integrated), and Intel Core i3/i5/i7 Sandy Bridge processors (Intel HD Graphics 2000/3000 integrated). All of them support MVC (BR 3D codec) hardware decoding. Just install the latest GeForce or Catalyst or Intel Graphics driver. That's it.
You need at least a 5*** series card for 3D.
But even you put a 3D GPU card:
You can't change your TV's setup when it's connected to an HTPC.
You must adjust it on your player or DVB Software.
If you want to watch live broadcast only ProgDVB Pro is supporting real 3D TV.
If you record first and watch later or if you want to watch your SBS files you can use Stereographic Player.