iMac G4: AirPort card or USB wireless dongle?

I have an AirPort card in my G4 iMac but it doesn't appear to give particularly fast speeds compared with the PowerBook (with AirPort Extreme card). One problem is that the AirPort card stops working if I browse certain web sites - there's one forum where clicking quickly from message to message can seemingly kill my internet connection and I have to switch AirPort off and on to reconnect (although the AirPort signal display stays at full strength).

I also have a D-Link USB wireless dongle which I've never used because I've heard that it's not advisable to connect it if there's already an AirPort card installed so... is there likely to be any improvement in speed and reliability if I remove the AirPort card and plug in the dongle?

Have you tried changing the channel your wireless router is transmitting on to say channel 4, stay away from channel's 1, 6 ,11 as the ones around you will be on them.

Bizarrely I spent ages recently finding a clear channel and positioning the router so I could use the PowerBook in the garden. Today I find someone has now started using the same channel as me. Have switched to a clear channel and will keep an eye on things.

But I'm not sure if that explains the slightly slower speeds and occasional cut-outs I was getting on the iMac, as I get good speed and no interruptions on the PowerBook.

I am interested to know if a 3rd party dongle woul improve the connection speed?