I've noticed they quoted for MLSG, that's good, they last a lot longer to crappy old paper type ones. I assume engine overheated hence HG failure. For STI engine I would say definitely. For WRX yes if you have the money, if you are skint and engine wasn't overheated too badly you might get away with just the gasket, BUT it's a risk.
I personally would not risk it.
I just had HG failure on my 03 STI, it cost me for complete engine overhaul ยฃ5k + labour.