I have no experience with the other two speakers but have a fair bit of experience with PMC speakers. I don't think you'll get a massive upgrade going from the GB1 to GB1i. The bass on the GB1 won't go too low due to the smallish drivers. If there is chance, try the OB1. This is the speaker that will give you everything from top to bottom and will sound punchy with the right amplification.
I've listened to Monitor Audio Silver series speakers and they don't sound too punchy -rather lightweight.
I've listened to Monitor Audio Silver series speakers and they don't sound too punchy -rather lightweight.