$4,500 won't break the bank. Are we talking about my bank or your bank?
Perhaps provide some specifics. 210 lb is hardly going to be a problem for most road bikes. Steer clear of wispy wheels for racer types but for the most part you should be fine.
You can probably also get along just fine on a 56cm bike, make sure you test some out. I'm 6'2" on a 58 but YMMV. There's more to fit than just height, of course.
What do you mean by "flips my lid"
Not all Treks are the same - which ones did you try? And Giant? Cannondale CAAD10 are nice bikes, or the supersix if you want carbon. Spec. Allez aren't too bad either, price wise. There are also tons of smaller brand bikes all over (Jamis, Felt come to mind) that may be at a store near you.
If you really want an inexpensive road bike and have some mechanical skills you can always try BikesDirect.com. Other options, head down to your local performance or REI and try out the house brand bikes.