I bought a used scarlett 2i2 about a year ago to use with amplitube 3. Lately I have noticed that it has a very bad connection. I have tried a couple different USB cables and nothing fixes the issues. It seems like the USB is just barely making contact to the focusrite and if you touch or bump it there is a lot of loud pops coming out of my speakers.

Is this something fixable or is the interface junk?

I found a used focusrite sapphire pro 40 (rack mount) on guitar center.com for $200. Would firewire give me a better connection than USB?
As far as connection - no, firewire might be faster, thus less latency. Usually the usb jack could be repaired but you might need an el. tech to do it, so I don't know it is worth the repair. I'd guess $40-$60 at a local TV repair shop.