Need clarification about Firewire

whaddup dudes! I've been racking my brain on this issue I'm having with Firewire. I use a iMac that only has one firewire 800 port. I've read so much literature and views on how to optimize hard drives for audio work and it's making me question if I should sell my iMac and save for a Mac Pro. I feel satisfied with everything else about my iMac but the Firewire issue. One thing I need real clarification on is whether or not daisy chaining devices over firewire, like connecting both my audio interface, and an external HDD, will affect the overall performance. If daisy chaining devices on my iMac doesnt hurt performance, then I'd rather keep my iMac. any good insight would be appreciated.

this exact reason why i ended up trading my imac for mbp, still has only one firewire port but it also got express card slot

Some interfaces play well with hard drives or other devices on the same bus, and some don't. It really depends on the interface and how hard you intend to push that hard drive.

Why don't you get a USB hard drive? I have a USB drive and a firewire interface hooked up to my macbook (not pro) and they work like a charm.