I think you'll feel a LOT more vibrations through a solid transmission mount than you'll feel with your solid engine mounts--you sit right beside the transmission and basically on top of the transmission cross-member, whereas the engine is a little more isolated up front. I've got a stock rubber mount on my T5 and poly motor mounts. I can feel a little vibration (not as much as solids), but not nearly as much as when the shifter base was bumping up against the tunnel opening (equivalent of a solid mount).
Daniel