okay here it is all layed out:

whether its a spring or coilover doesnt matter on the ride. What matters is first of all the spring rate and the wind of the coil. Progressive has a loose wind at the bottom and a tight wind at the top, that way when the spring compresses it becomes more rigid...and provides 'better handling' but is more unpredictable in serious cornering situations. Progressive springs yield a better ride in the city because the lower portion is similar to that of a stock spring. Linear springs are all the same rate, and usually provide for better handling when coupled with a good dampener. Coilovers come in linear designs only, and allow for ride adjustability. Dampeners have more of an effect on ride then the actual springs/coilovers do. Springs affect the way the car moves front to back and side to side, and without dampeners they would just bounce forever. Getting an adjustable dampener is a good idea when lowering considerably.

and yes strut tower bars do help... well if you get a good one. some of the brands like DC sports have flimsier metals and tend to bend abit more then other brands like skunk2 etc. its just another piece in the suspension pie...having them certainly helps and its an easy way to give the suspension that extra rigidity without forking over big bucks for something more extreme like a cage.