I don't know much about capture hardware, but there's always going to be a limit on the number of effects you can have before they start to bog the system down.
I use the Matrox card which has good colour correction and with my system which is now 3 yrs old i can get 6 layers in real time ( depending on effects used ) i find it very good !
I have the Matrox RT.X100 Xtreme Pro and I can mimic most of the Magic Bullet looks with Matrox's CCing in realtime. No rendering at all! It's awesome. Plus you can get a free upgrade to Adobe Production Studio Standard (the latest Adobe bundle).
And you can layer a few other effects before you need to render.