Michele uses a Japanese Jazz bass with a G printed on it from a previous band name "Guess". The bass belongs to the bass player from that Guess. Michele simply retained it when the previous player left the band prior to the formation of the magic numbers.
The Gibson Amp belonged to the magic numbers manager, a session guitarist called Paul Noble, (previously of the Warm Jets). The amp is designed for guitar featuring a 10 inch and 12 inch speaker. I believe it is called a "Gold Tone" These amplifiers suffer from power supply problems and often require a complete replacement transformer of an enlarged size.
see here:
Gibson Goldtone Tube Guitar Amplifiers Hands-On Review at Musician's Friend | Musician's Friend
After some touring with the British band travis, The Magic Numbers employed some of travis' technicians and a michele pursued an endorsement deal with Orange as a result of Travis' Bass tech's relationship with the brand. I too believe her tone suffered after moving to Orange. As I understand it, the reliability of the orange amps made it tough for the band to use on tour and often the orange amp would be set up on stage, but with an ashdown amp setup behind it and plugged in.
Michele uses avalon DI's in the studio.