If it was me I'd stick with a 1.6 and go with a turbocharger.
Otherwise, a 94-7 1.8 with a 99 head would be the best combo.
Keep in mind, the performance difference between stock 1.6 and 1.8 is very slight.
The 1.6 enjoys the high revs while the 1.8 is more 'thrashy'.