There is no real advantage to installing solid motor and transmounts. The stockers are in no danger of breaking, especially at your power levels. Solid mounts will certain transmit more vibrations to you. In short, it's a waste of money and won't give you any substatial benifit.
if anything i would go with polyurethane mounts. i just installed them on my motor and i need to get the poly trans mount as well. i am using them to help control some of the wheel hop i have with the IRS.
Yea there is no way you NEED solid mounts. Do you have any idea how rigid they are? They would make driving your car very uncomfortable. At most i would do the polys. Stock replacements are probably a better bet with the mods in your sig
i had my mounts welded together at one point cuz i was too cheap to buy new ones... man i'll tell ya what a nice comfortable acceleration was.. turned into a grinding jerking feeling..