Ade_WRX

Started up my 95WRX this afternoon and heard a knocking sound coming from the back/mid engine.
I am thinking the worst!
I bought the car only 2 months ago, privately 62k on the clock.
I only use esso super unleaded petrol and thought the engine would run ok on this fuel or am I wrong?
Spent £600 on a new timing, ancillary belts, pulleys,tensioners engine/dif oils and yes, i did disengage the crank sensor/ fill the oil filter etc.Mobil1 15w 50 /castrol syntrax.
The wife is giving me jip over it, saying I told you so, you shouldn't have bought such a old car.
I feel physically sick and feel like blowing my brains out!
Anybody have any ideas on the cost of a replacement engine/ overhaul.
Or could it be something a little cheaper.
My luck is pants.

cheers
Ade