I find PC International to be at least 10% cheaper than IC, sometimes 25%, or even more.
But yes, they charge a fee if you pay by CC - I always pay them by cheque.
IMO IC are a hopeless operation, I don't know why they don't model themselves on one of the North American chains, such as Futureshop.
But I also import computer stuff from the USA - but only when it makes financial sense. At the beginning of last year I got a P6T, i7, and fast DDR3 RAM from the USA, at the time most shops didn't stock it here and the ones that did were too expensive. PC International didn't keep i7 CPU's or motherboards at the time.
Or do an EFT and send them the deposit confirmation - that's the way I do it with them and then you don't pay extra for a CC