engine upgrade

i have a 1986 1.8gti and i want a new engine in it the old one is tiring, any one any ideas what i can put in it. :dontknow:

How much money do you have?
How much power are you looking for?

Have you searched around the site, this question is asked 100s of times!!!!

the old one just feels tired ,and i have read i can put a 2ltr engine or bottom end on it to freshen it up as for money its i dont mind paying as long as i get the improvement in performance.i am new to this site to i am still looking around.are there specialists on here that deal with engine upgrades.