i've done that exact mod, and i firmly believe it was the biggest improvement in my car for the least amount of money, making it the best mod i've ever done on my sx.
it gave the car new live, brought it back from the dead so to speak.
its a difficult job, one made much easier if you have a hydraulic press, but its totally possible to do yourself in your garage with minimal tools. a decent bench vice is necessary though, if you dont have the press.
my sx, after i installed the bushes, was hundreds of percent more responsive, with suspension being tons more accurate. turn-in was instantly sharper, there was instantly less bodyroll, and everything firmed up a little.
the ride, of course, was more jarring, but its not uncomfortable, and only takes a short amount of time to get used to.
i bought the black ones, and the kits is totally complete (they even include bushes for the steering rack mounts), and only two of the subframe bushes didnt fit (unless i'm just an idiot - possible!!!). the lubrication supplied with the kit is hardcore, and has lasted me more than a year without a single squeak, and with complete reliability.
i bought mine from summit racing at US$139.00. but that was local shipping in the states. you would pay extra for international shipping.
also, i searched for many polybush kits for the sx, and the energy suspension was the cheapest in comparison.
for example, the kit from powerflex.co.uk would have worked out to R7500.00 without shipping, and i only paid about R750 for energy suspension!