This is a question that even I asked recently and the best answer I can give is that its a matter of taste. I really dont get how adding overload springs would enhance handeling or even stiffen the suspension, but if it worked, hey. My understanding, fromt he IPD guys, is that they have a stock spring rate but are longer so that more weight can be loaded into the back. They were designed because the stock volvo springs dont allow much of a load and a full family in the car without bottoming the springs. The springs that I have on my car, just got them, are the IPD sport springs. I chose them for a few reasons. The first is that IPD is a great company to work with, they have the best customer service around, knowledgeable staff, and I have done business with them before. Another reason was because I was assured they would fit without issue and would not mess up the camber on the car beyond adjustment. One thing I have seen on too many cars is people going with aftermarket springs that cause excessive camber problems. They are stiffer than stock by a good amount, which will stiffen the suspension and improve handeling, but not so much so that they feel harsh. They make for a nice agressive look on the car which is cool, but really not why I bought them. I also baught a set of Koni adjustable shocks. These Yellow numbers are the only shock for my car that offered manuel dampening adjustment. Its not real important to have this, but I thought it would be nice, especially given the car is my daily driving. I have heard that Bilstiens have automatic adjustment, but given there is no electric motors or sensors in them, I think that just means they are progressive. I dont believe they will litterly increase dampening because Im driving on a smooth racetrack and need maximum dampening. Because I do a lot of racing schools and track driving with my car I felt they would best fit my needs. Price wise they are more expensive than Bilstiens and not really of any better quality, but I felt it was worthwhile in the end. The last product I have purchased is a strut brace. I bought this after a big warning from a local Volvo shop. The mechanic said that the 850 chassis was just not designed for the stress of such a stiff suspension or the agressive driving it will get. The strut towers flex alot durring cornering and have been known to crack along welds and bolt holes. I saw a confirmation of this when a guy with lowering springs on his 1994 850 wagon had these cracks. I bought the strut brace to reduce the chances of this happening, and I have been told that I should not have this problem with the strut brace. Another advantage of the strut brace is that it removes the last bit of play in the suspension and makes the car handle that much better. Anti-sway bars and urathane bushings are next on my agenda of suspension tweeks. They will stiffen up the suspension even more, reduce body roll a good amount, and allow me faster track times. Plus the bragging rights, hehe. I take driving school at Watkens Glen BMW club race school and so I mostly race against BMW's when Im up there. The stock car held its own against new 3 series, new 5 series, older 3 and 5 sersies, and older M3's, but I was killed by the new M3's and M5's that are up there. The new suspension tweeks have allowed me to run with the M3's no problem, given that most of us are all equally good drivers and I know my car isnt as fast as an M3, I have to guess that I can way outhandle them. Maybe with the chip, exhaust, boost controller, and a brake upgrade I will be able to rule the track, hehe. Its a dream right.