Would Outback Sport suspension fit? That would probably be the best bet. Would actually raise it up a bit. If not then RS/TS suspension. Maybe you could find somebody over on I-Club....er....NASALOC....er...NASIOC to swap suspension with you.
This thread illustrates that everyone DOES NOT have the same opinion on everything. Most of us are looking to stiffen up the suspension! LOL.
I saw a video of a bunch of rally footage. There was one scene where the WRX jumped this hill. When it landed, it looked like the body stood still and the shock was absorbed by the suspension. By looking at the jump, you would assume that body would take a lot more on impact. Is that the result of stiffer suspension? How would stiffer suspension handle everyday bumps/potholes? =)
Lousy. The problem is you need very stiff suspension to take big hits, but softer to smooth out little bumps. Those cars actually have both - to an extent - by having coilovers that can be valved differently depending on the speed of the suspension movement over the terrain. You'd still find a ride in one of those cars to be incredibly rough.
A possible option might be a set of custom-valved coilovers on soft progressive springs. Most come setup for performance, but can often be re-valved to behave differently. You're talking $$$$s though.
The thing you're really up against is the fact that aftermarket suspension parts are designed to increase performance, not comfort. There's just a much bigger market for performance enhancements. A set of progressive springs would do the trick, but they're all stiffer than stock and the stock struts are too stiff for that to really work. The stock springs are actually pretty soft.
tough question...are you looking for better handling or comfort? In general, better handling equates to a stiffer ride.
But if you want the best of both world, ask someone with the LATEST dms40 and ask for a ride. Then you'll need to wait six month and go for a ride again. If you see/hear no problems then that would be my recomendation.
Others who have switched to the STI struts do mention that it's similar to the dms40. You might want to see if someone have them near your neck of the wood and go for a ride. A second ride won't be necessary should you like the STI struts.
Another setup is the Tien with close to stock spring rates. Someone here (southern Cal) has this setup with Tien RA and likes it alot after dumping his dms40. I might give this set up a try when the funds become available.
You might consider changing your struts. The stock struts are a mono-tube design that end to be a bit stiffer riding, especially when it comes to compression damping. A good twin tube strut like a kyb would offer more even damping and a perceived softer ride. I noticed that switching from the stock mono-tubes on my old sentra se-r to kyb agx's gave it a much smoother softer ride. Hope this helps...
Hey, don;t forget tires. Call TireRack and tell them what you are looking for. This may be the best fix.
If a harsh ride means, that intial kick you get from hitting a pot-hole, I don't think better struts will help that. Stuts control the occilation in the spring. So, better struts won't do anything for that first hit, but how the car recovers from that may improve.
The reason Rally Cars can take such a huge jump with no problem is because they have a ludicrous amount of suspension travel (WRXs have nine inches of it, stock). The WRX suspension has a stiff intial impact and long travel. It basically means when you can drive off a three inch curb and literally not feel a thing. As for smoothing out the ride, your best bet are shocks as other people have suggested. If you want to beef up the handling, swaybars (but not springs) would reduce body roll without affecting straight line ride too much.