K'nex released an engine powered roller coaster a few years ago with a loop, sound effects and all (the figures in the wagons would litterallly scream) - I got mine at TRU after a Christmas sale in 2003...pretty awesome but all of those pieces are a pain when putting them together...Size wise klickies are not compatible with the coaster's wagons, such a shame.
PM's Japanese roller coaster is very pretty...if i remember well the last (and only) time i saw it on ebay (about 2 years ago i think) it went over 1,500 USD...if it's ever re-released (which is very likely after so long) such a strong investment would hurt, ouch