Not really, If he picks an AM2-system he only need to upgrade mobo+CPU and that is cheaper than upgrading a graphics card.GPU upgrade is easy....CPU, Motherboard, RAM - that's major.
Get the Core 2 system, you'll thank yourself when in a year or so and you want to get the best out of your system you only have to buy a new graphics card rather than a whole new system.
EDIT: sorry i missed the multi tasking, um, first what kind of multitasking? like word and music or games and encoding at same time? the intel one is dual core i think, but is that athlon a dual core? if it is, the athlon will be good for multitasking and even better for games.