The price in your country are far higher (usually) then here.
With a 4k budget I think you would be hard pressed to do the 2.5 with a turbo swap and tuning.
You can get a 2.5 shortblock from subaru for under 1800 last I checked. You have another few hundred tied up in gaskets/waterpumps/misc. stuff. I assume you would be at around 2,500 at this point left over for turbo/tuning/labor. It could be done but I think that would/could stretch your budget depending on how much stuff you have to outsource. You might be able to get a few hundred for your killed ej205 which might help.
Have you budgted out what a rebuild on the ej205 would be?