I think you are off track. GearBox sounds great to me, and so does POD Farm. I have the Toneport interface, which is in my opinion very good as an audio guitar interface. I get great tones with my guitar straight into the Toneport. This rock solo video I made is using only Line 6 Pod Farm for the sounds, and the guitar is a cheap $400 Michael Kelly.
So getting good sounds out of a $99 audio interface via GearBox sounds very reasonable to me. I don't know of an amp that can give so many cool sounds for $99. Plus, you'd need a microphone and recording interface for that too...
I don't know anything about GuitarPort, so are you saying it doesn't work with GearBox or Pod Farm? If so, just return it and get the Toneport GX or an older UX1 like I have and be a happy camper.