The Champion RS171 would be a candidate, the M3 looks good with straight spoke wheels, or subtle Y spokes. The RS171 may look better on our slightly chunkier cars with slightly thicker spokes. The rear wheel on the 997 looks beautiful, purposeful and spare. A satin gunmetal finish would be good on lighter cars, don't like this wheel as much in silver.
for inspiration, HRE P43, another great looking straight spoke wheel. I saw this in black on a 997, it was a very strong and elegant setup. The look is a distant cousin to the OEM 19". I bet RAC could design an even better looking version of this general design.
The RG4 still looks superb. I don't think this style of wheel is ever going to look completely out of date.