I am in a similiar position, except custom is out of my price range at the moment. I'm assuming you work at a shop to get the fat discount on the Cannondales. The T800 would be my last choice, if you are paying retail I could see $300 difference between it and the T2000 giving one pause, but at 1/2 off the $150 difference makes the decision between the two a no-brainer.
Between the T2000 and a custom I'd say the only question is how much you can afford. If you can afford the custom, then go for it. Your bike will fit like a glove, it will be have exactly the features you desire. A custom lugged frame will last a lifetime (not that I'm bagging on AL). To me the opportunity to support a craftman who still builds things the old way--slowly and with superior quality---is rare in this day and age.

Since I can't afford a custom bike right now, I will be buying a T2000 with my bike shop discount within a couple of months. When I can get a custom frame I'll put the parts from the T2000 on it.