A "more 'relaxed' performance geometry" such as the OP asks about sounds to my ear like he's looking for the type of racing frame that was designed for distance road racing as opposed to closed-circuit criterium racing. The options are legion.

Quanckenbush: I can tell you from experience that a Lemond frame with Reynoklds 853 tubing is likely to be exactly what you are looking for. If you are big enough for a 61cm, I have a 2000 Lemond Zurich frame, fork and headset that would do you proud.

As for Lemond steel models of the late 1990's-early 2000's, the frames were the same (with one exception), with the model differences being dictated by the componentry. Mine rode great, cornered like it was on rails, and was good for the whole day. The exception, the Poprad, was made for cyclocross, and thus is likely to have somewhat different geometry (higher bottom bracket, cantilever brake mounts). But the Zurich, Buenos Aires, Chambery and one or two others had the same frame, and it's a good one.

As for other marques, brand name alone isn't going to tell you much. You need a tape measure. Look for chain stays in the 40cm range and a wheelbase of 100 to 101 cm. That should give you the performance you want without the bone-jarring bashing of an uber-stiff crit bike. These measurements are probably the best single indicator you can easily get. The other factors have more play in the joints.

Ideally, you should also get the frame angles, especially the seat tube angle. For that, look for 73 degrees - that is not carved in stone, but it is a very good place to start for what you are describing. The headtube angle can range from 71 degrees for short riders to 74 or even 75 degrees for tall riders. If you are in the middle range for height, a frame with 73 degree headtube and seattube angles is a pretty good bet.

Frame material can also make a difference. For example, a classic Reynolds 531 frame is likely to have more flex than modern super-steels of the same geometry, and Columbus SLX or SPX will be stiffer than Columbus SL or SP because of the "rifling" ridges in SLX and SPX. There are way too many variables between tubing makers and their various products to discuss them all here (and I don't begin to know all of them or even very many of them), but the tubing will have some effect. And if you have questions about some specific tubing types, someone here will be able to answer them.

Good luck in your search. I think I know the kind of ride you are looking for, and you will like it when you find it.