(unfortunately) The best for those springs would be the Skunk2 shocks, or better option, Koni Yellow Sports(there is a sale for $350 shipped for these going on now btw on this site).
Those springs lower the car quite a bit for just being lowering springs, which means they have higher spring rates than most other lowering springs. With the drop and the higher spring rate, you need proper shocks to match. The Koni STR.T's are meant for a mild drop with mild spring rates, I believe Koni even says that about them... The Eibachs are probably around the same ball park. So they really shouldn't be used with them.
The ride will be uncomfortable either way. If you go with under damped shocks like the Koni STR.T and Eibach would likely be for these springs, you'll have a bouncy ride. With such a spring rate, the proper shocks like the Skunk2 or Koni Yellows for these will mean performance will be better and around where it should be, but the ride will be rough.