Coolermaster Extreme 650W

is this PSU any good im not sure it is about mid priced an can i put it on the Gigabyte Poseidon case any help would be great

See if you can get the Real Power Pro 650 watt one from Coolermaster. I have that PSU and it's great!

The eXtremePower 650W is a rebadged older model Seventeam 500W, with +12V@30A and reasonably low efficiency. While it's still a reasonably good quality unit, make sure it's priced appropriately for that, and don't expect it to provide 650W. Coolermaster's Real Power Pro series is better, and there are more recommendations at ceewi1's PSU Recommendations