I'm looking for a not too expensive lugged steel frame to build into a "fast" commuter bike. I thought I narrowed it down to the Soma Stanyan, but I just saw they also have something called a san marcos that looks pretty nice too.

One thing I don't get is the double top tube on the larger sizes. Seems to be something Rivendell bikes does but plenty of other makers of larger frame sizes don't do this and even the Soma Stanyan doesn't. It says it's to "restore the triangulation lose with the tall top tube" but I don't see any loss of triangulation in other "tall" bikes. What are they talking about?

One a more general note, any thoughts on which of these would make a good commuter bike for 30 mile RT rides with just a rear rack and maybe 20lbs or less of "stuff" to haul? I will put on a drop bar and compact crank with probably an Apex 11-32 rear cassette. I will most likely get a 60cm (Stanyan) or 59cm (San Marcos). Geometry on the Stanyan seems more agressive with the short HT but not sure I care about that.

Thanks.