Also, re. "planing" vs. "noodly", I personally find that bottom bracket flex doesn't bother me, but top tube flex does. IOW, I don't notice BB flex, but TT flex can result in a bike that handles weird and is always calling attention to itself. In a 54 or 55 cm. frame with an appropriate length top tube, my opinion is that with your tubing selection you will get the "planing" Jan talks about, without the whippy feeling on the front end that can be so annoying.

Oh, and you are right about heat treatment - it makes the tube more resistant to denting (and also allows it to put up with more cycles before failure) but doesn't affect flexibility to any significant degree.