Ever thought of doing the 20v Turbo conversion. Tis the future!
On your budget you can do either. The 2.0 16v will be the cheapest and easiest by far. You will only need a hundred or 2 to do it. With the rest of the cash you could get the head ported and polished, 4 branch manifold, etc etc. I bet you could get close or past 200bhp from a 2.0 16v with that money.