DOHC is only worth some extra marketting stickers to the car manufacturers. You can run both 2 and 4 valve/cyl heads from a SOHC, and you can make a more compact head by elliminating rocker arms in DOHC configuration, but when you get down to it, all DOHC really means is that you´ve got two cam shafts, whoopty dooo.. unless you´re planning on adjusting the cam timing on each shaft independantly then the differences in engine tuning abilities are slim. Variable valve timing can be made more efficient with DOHC than SOHC, but we don´t have that do wewas thinking about turbo´ing my 1991 Geo Metro 1.0L until I wrecked it, but in retrospect it was a SOHC and it might not have done well with the extra volume of air going into it.
[/TD][/TR][TR][TD]dohc motors are quiet, sohc motors are loud. turboed motors are generaly quiet as well.