Stiffer/ dual springs have a few downsides, including considerably increased valve seat, stem and cam wear. They're mostly for all out motors where long term reliability isn't the main driver.
The point of them is to prevent valve float with high lift cams. The beehives and titanium retainers are mostly to counter the effects of the weight of the additional components in the valvetrain. Again, nice to have, but mostly for all out, high-rpm racing.
I'd stick to the 40a and single springs for the street. The higher lift cams require valve guide trimming and double springs. Pgilles runs his 40a with stock springs and reports no issues. If you decide to go this route make sure your stock springs are on the high end of spec.