honestly, I dont personally own a speed3 but I have done a fair bit of work on 'em......I have ridden in them stock, with the delrin mount, and with the TRZ and to tell the straight truth, you can NOT even tell the trz is there, the delrin is more noticeable but not that bad....it goes away almost completely when in gear and at idle is more of a VERY soft -rumble- than a vibration
granted I dont daily drive the ms3 but until you ride in a car with stiffer mounts all around you dont know what vibrations are =P
personally my msp has AWR front and rears with a SLS Performance passenger side (all three had originally torn) and while those vibrations are bad in a cold startup they go away almost completely while doing normal driving as well
my recomendation:
find a local with a trz mount and ride in it....only you can tell if its going to be too much for you, a lot of people on the cali forums get the mount thinking they are gonna hate it and then end up loving it