Yea, i'm not saying there is absolutely 0 bottleneck...however, like you said it is over rated. An older cpu is no reason to plop in a crappier card because someone says this won't be any benefit.. Get the best you can within reason.
For example, if my system was pci-e, I wouldn't pair my 2.8 p4 with a 8800gtx...That's just overkill.