What you do with the dampers, springs & swaybars will also vary based on how much you brace the chassis with upper & lower Strut-Tie Bars & K-members/brackets or the like.

*****One of my cars benefitted IMMENSELY from a simple front lower tie-bar.

So @niky’s mentioning using Ties to stiffen the chassis is Very important, even though your question was about springs+dampers.

Ultra-Racing, based in Southeast Asia, makes tower strut-bars, chassis braces and anti-roll bars for a whole host of Korean vehicles that are not supported by the aftermarket. Sure, you’ll have to pay extra in shipping, but their products are of very good quality.

http://www.ultraracing.com.my/Catalog.asp?Brand=Hyundai&pageno=4

They apparently have two levels of anti-roll bar for the Sonata, but I don’t know if they match your model year.

I find that the best cars in terms of a balance of handling and ride comfort, tend to have a very rigid and well-braced (and, preferably… light) chassis matched with relatively soft springs and modest dampers. It also helps if they have lots of suspension travel… too low and too little suspension travel can be just as bad as too tall…

You get ride height adjustability.

You get damper adjustability.

You get a spring matched to the damper.

You get a higher spring rate but often the ability to soften the ride for the street and stiffen it for the track.

They’re worth the money every time.

The car is a daily driver. My aim is to get it to roll less and turn in faster. A little lowering is okay, but I’m not looking to slam it.

I had been looking for thicker sway bars, but in my research there aren’t any manufacturers that make sway bars for the Sonata that aren’t more aggressive than stock. I did, however, find that K-Sport makes adjustable coilovers for the NF Sonata and asks $950~ for the set. Eibach and H&R only make springs for the model, however, they only ask $300-350 for them.

A mild upgrade is almost always best.

The front lower control arms should never be pitched above the horizontal (ie: ends higher than inboard mounting pts) when the car is at rest, or you lose your geometry while trying to get the stance + lower cg. (this was for a VW, mind you, but the concept still holds, iirc)

Other recommendations I got were to: not lower the car much more than 1.4 inches, not increase swaybar diameter by more than ~15%, don’t go thinner than 50-series tires, don’t wheelspace out more than 8-10mm rear, 5-8mm front, and to use shock+strut+spring kits rather than mix/match.

That’s just a guideline. The total setup for what you want to do will probably vary wildly.

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+ I believe the classic Lotus setup is softer springs and stiffer swaybars.

I prefer coilover for quick adjustments – as Sajeev says you can more quickly adjust height to help corner balance the car (by adjusting height you can help the car turn left and right at the same capability (most cars cannot due to weight distribution and factory settings). However if you race in series where cars are required to keep their torsion bar suspensions – it makes it a real pain in the butt trying to index a torsion bar versus a coilover setup. Like my 944 Spec car.

You also have to take into account how progressive the coil spring is – most coil springs are set to be initially softer when it is first compressed then they will increase their tension (become stiffer) the more it is compressed – giving you a smooth ride for small bumps yet absorbing the large bumps without crashing into the bump stops. Most coilover springs are not progressive and provide the same tension across most of the the spring’s compression – giving you actually greater control but the ride is harsher for normal driving (small bumps can rattle out fillings in your teeth). Plus another beauty of a coilover setup is they often come with adjustable shocks that you can use to damper the spring. Some even come with inner springs to supplement the outer springs. Then you get into remote reservoir setups, blah, blah, blah.

The main benefit of coil overs for a street application, imho, is that you can get that ultra low stance. If thats is what you are looking for they may be the right choice. Get ready for a horrible ride and having to pay to have the car corner balanced every time you need an alignment, though.

Personally I like my car to hit a compression with minimal drama/pain, but then immediately damp it out. The stock springs aren’t going to help make expansion joints comfortable, but anything bigger than that remains civilized. Also, I like some lean going into turns, not a lot, but I think a bit helps me judge my lateral load without always bumping up against the oversteer/understeer limit. Although, that’s a lot of fun too; for a while I was running lowered springs on my car in comb. with my dampers and it was a beast, but not a fun ride 80% of the time.

It should also be a lot easier and cheaper to find a damper designed to run with the OEM springs, and customer feedback for the product will actually be relevant to your purchase, as they aren’t running a mystery spring setup in concert.

I find that water is the best dampener, tho beer will do in a pinch.

I’d like to add… while the quality of stock shock absorbers is all over the place, the quality of lowering springs, both in terms of proper stance and ride height and proper stiffness, is an even bigger spread.

Most cars ride horribly on “lowering” springs, with the exception of some sports-cars or “sporting” model variants which have stiffer dampers, as standard. I actually prefer going with adjustable dampers, as these cost less than coil-overs (and you don’t need the range of height adjustments these give anywhere but the race track) and maintain some semblance of a good ride.

In fact, some cars do perfectly well with non-adjustable replacement dampers.

Some forums have info on the spring rates and ride harshness of various aftermarket springs for the specifc make and model the forum caters to. Good for you if you can find one for your car… sorry if you can’t.