Go with a good US based host. Your current provider is absolutely one of the worst in the industry. This is my personal opinion of course, but their support, hardware, and networking have gone awful. Look for cloud VPS providers. Even their cheapest $5 can easily outperform shared hosts.

Second, choosing an AU provider might help to bring the the TCP round trip time, but in most cases, it is your application itself that is the bottleneck. You can test the pin times yourself, and I am think providers in US West coast and Singapore can give a reasonable sub 150ms ping time.