Won't add much, but:

You are around 170lbs, want stiff, but are thinking about a 24 spoke rear. Simply does not compute. Thinking the same on the Sapim Super spoke, 1.4mm diameter, yikes that is skinny. The spoke may be strong enough to take it, but I can assure you, as an engineer, it will come with the price of increased deflection. While different steel compositions, heat treatment and processing affect strength, they do NOT change the modulus, which defines how much a material will deform for a given stress (Hookes Law). For a spoke, assume it is only under axial tension. Therefore, Stress=Force/cross sectional Area. Cross sections, by my calculations: (1) Super Spoke= 1.54mm^2, (2) CX-Ray=1.98mm^2, (3) Sapim D-Lite, 1.65mm round=2.14mm^2, (4) Sapim Race, 1.8mm round=2.54mm^2. You are automatically taking a 30% hit in stiffness in going with Super Spokes over CX-Rays, all other things being equal.

Pdedes is making some reasonable points. From a strickly physics viewpoint, a little extra mass comes into play under acceleration/deceleration, not at steady state (ie constant velocity). Aerodynamics is always in play, albeit not that significant at lower velocities, and resistance is proportional to velocity^2.

Carbon rims don't make much sense with your financial limitations. Simply destroy one rim, pothole/whatever, and you are suddenly looking at an $800+ repair. Do the same with the C2 rim, and you are back in action for $150ish.

FWIW, working with pre-preg carbon fiber material, which is what the Enve rims are made from, is nothing like working injection molded plastics. Most of what the general populace considers "plastics" are thermo-plastics. The are solid at room temperature, apply heat, they soften, and once cool, they harden again. Pre-preg, is short for pre-impregnated, as in a fabric, woven or not, of carbon, or any number of other fiber materials, loaded with a resin, in this case epoxy, which is a thermoset. Flexible, at room, or lower temperatures, to be cured at elevated temperature. Once cured, they do not soften again, although they can be damaged by heat. The stuff is terribly expensive, and somewhat of a pain to work with. You don't just slap a couple of pieces in a mold an call it a day. I would not be at all surprised if Enve has 60-90 minutes of labor in each rim.

Go ahead an purchase the nice alloy clincher set. If you really want to experience the Koolaid, think a set of carbon tubulars, with some Vittoria Pave EVOs (24 or 27). You could hit your weight, stiffness, and performance goals, and ride what the pros ride, if that makes any difference.