Budget is budget hey. Also, you did not test the STR500's properly IIRC (remember I gave you the settings [that made a massive difference] to try?). No fiddling with settings and no proper testing environment. Obviously the Jamo's are better, but they also seem a lot better to you because they are in your home - a smaller space with better acoustics.
Sure, if budget is R8,000+ then go for a better amp and entry level Jamo's. Though I still maintain that STR500 is a big enough upgrade for most people, and for most people audio over optical isn't a train smash (one extra already hidden cable). Plenty of people rave about them, no question they're the best for a R4,500 budget.