Basically, when you hit a bump...the Spring is what allows your car to compensate...but if you think of physics, when you push against a spring, it'll push back...overextend, recompensate...and go back and forth continuously until all the energy is returned to normal. So, obviously if your car only had springs, any bump on the road would make your car go crazy. Shocks primarily control dampening...which is basically absorbing the energy from going completely into the spring. Shocks eliminate (as much as possible) the "back and forth" that the spring would otherwise create...returning the car back to neutral stance after absorbing a bump/ditch.

Now, you want to get aftermarket suspension...springs that lower obviously have to be more progressive...think "stiffer"...because if it was as "soft" as stock springs...it would need as much distance to travel to absorb a bump
(otherwise you'd bottom out and tear apart your car on big bumps). Keeping the increased progressiveness in mind, the shock must now do the same job as before and be able to dampen the bump and return car to normal. Since the springs are more progressive...the shocks have to do more work...stock shocks aren't designed to handle that much compensation...(in fact, this is good because high dampening also = less comfort).

Adjustability for shocks just means you can control the dampening rate...how "fast" you want your shocks to compensate for the spring movement/return car back to normal. I personally love this feature and that's why I chose koni yellows...

SO, in the long run, you will need aftermarket shocks to go with your aftermaket springs...simply because the stock shocks will wear out. Some people can get away with just keeping their stock shocks when they dont' lower too much...it's just wearing out the shocks slower... The lower you go, the more progressive the spring, the more work the shock must be able to do. Koni Yellows are great and very well designed, people go 2"+ with them and have no problems...but if you are only looking to lower ~1.2", koni reds or tokico blues etc would be fine. KYB AGX are also GREAT shocks and they are very well priced for adjustables. A friend of mine had these with Eibach Sportlines (2.2" drop) and it ran fine...going on 2 years now.

Hope this helps! Good luck with your mods.