Unfortunately, while the D16 has alot of options for getting some power out of it, none of them are cheap. At least, none that will produce some real power.

Normally I would just tell you to save your dollars for a B Series swap, but there is an option that (in my opinion) is worth considering: a Jackson Racing supercharger.

Some might flame me for this, but hear me out. The kit for your (or any D series motor) will come with an intake for your current engine/head. Jackson claims that the supercharger will give you somewhere in the neighbourhood of about 40%-45% more power. On a non-VTEC D series that's about 140-145bhp (VTEC D series would be about 160-175bhp). But the beauty of the supercharger is when you finally decide to upgrade to a B series motor, you can call Jackson Racing and buy an intake for your new motor (and whatever else you might need for the swap).

I will be honest, I don't have any experience with supercharging (on a Honda or otherwise) so I don't know about reliablity. But I'm sure there are plenty of experts on this forum that can provide you with all the info you need.