best suspension change for ph1 172

[therealMAtt]

Hi iv got a ph1 172 with standard suspension setup, i would like to improve the handling, with peoples opinion what would be the best option for this.
Some Koni adjustable dampers or some coilovers, my price range is about £5-600

iv read a bit about the FK coilovers are they any good, arent there 2 type to choose from!

thanks matt