During the Xmas sales I purchased the Korg Gadget plugins for Mac/PC as I have previously toyed with them on an iPad and felt they were a better investment of my money than the upgrade from Korg Collection Legacy Bundle to Korg Collection 4.
There are some excellent plugins in this collection… a very usable B3 emulator, acoustic and electric pianos, a Clav, virtual interpretations of the M1 / Odyssey / Wavestation / MonoPoly / MS-20 / PolySix, a PCM synth that seems similar to HD-1, a bunch of drum sample players, a 303 clone, analog synth drums, some arcade sound-chip synths and some cool Multi-FX processors for guitar and bass.
They have limited tweakability, but represent really good value for what you get. So far they are playing very well with GP4.
More info here: