Corsair RM is the most expensive despite it uses all-Chinese caps. I haven't much info on Gigabyte P-GM ATM, but now it's obvious that you shouldn't buy this unit. Seasonic Focus GX is 10$ more expensive than SF Leadex III and Bitfenix Whisper despite offering somewhat lower performance but really i didn't recommend it because Seasonic had some problems with high-transient power draw GPUs and it's still not clear if Focus GX doesn't have them. Corsair TX-m is the cheapest but it's also the least quiet unit there, so it's worth paying 5-10$ more for the other two IMO, SF Leadex III and Bitfenix Whisper M. I can recommend them equally but Bitfenix probably shoud have better consumer support in Europe (Portugal), not idea about Australia tho.