I'm with BJ Hines on this, essentially the S30 was a superior design at a budget price. Just as importantly it was reliable, easy to work on and durable, something it is still today and certainly something Euro cars in general were not.
Today it can still be made to go fast and on a comparable footing compete with Euro cars originally costing much more. As to the soundness of the basic design, just look at the S30's featured in this forum.