Coilovers and upgraded Anti-Roll Bars sort out the weight, mine feels alot lighter now and no Understeer... And deffo no floatyness...
Your right about it needing a bit more power, a piggyback and a tune sort out some of the power and get it down in the right fashion... Turbos and SC can be a bit costly to install and keep up, so its quite a high £ to power ratio...
Oh and your right about the sub, I didnt have one before, now have a JL in the bose space and its at its lowest settings... Speakers need an upgrade, mine sound 100000 times better now!