I don't think I'm being a fan boy if Intel CPUs are clearly faster than AMD (at least right now, with current generations).
Sure, AMD is cheaper, but also significantly slower.
If AMD were faster, I'd be recommending them. (and I have in the past, when they used to be competitive speed-wise)
As for cost, if you're going to spend the money on a machine that is capable of multiboxing (especially 5), I don't think an extra $100 (or so) for an Intel CPU is going to break your bank.
In fact, I'd advise cutting costs in other areas to get an Intel, if cost is really an issue.