The amp simulators in Logic are pretty damn good! I don't know if Amp Designer comes with express, but it deffo comes with Pro 9, which is about £120 ish on the app store. Plus it's amazing for everything else, great recording DAW.
Fantasticly easy to use too - just add it as in insert on your track.
Personally I prefer Logic as a DAW to even Pro Tools.
If you can stretch to it, you'll never regret it.
As for an interface, the JamVox seems to function as USB input/output so yes it should be fine. Wouldn't like to comment on the sound quality though. If you decided to buy an interface, you'd need a DI box to let you connect your guitar straight into the mic inputs.