Though I'm very new to multiboxing myself, I tend to think if you're going to spend the dough (and you can't avoid doing that in multiboxing) you might as well do it properly.

While there may be other alternatives to recommend, so far, I've been very happy with Keyclone.

I'm not sure about the hotstrings thing (@ work not home @ the moment), but as for WoW, opinion seems to be divided on whether you get better performance by just copying WoW into another folder and using 1 copy per account, or running all accounts on one installed copy. Personally, I've made 5 wow folders (the last 4 just being copies of the first one).