Stick with the 1G head with the 1G block. I haven't heard of any signifigant gains with a 2G head swap. Just seems like more headaches. Lots of DSMers I know that own 2G models will love a 1G in there car. 1Gs don't have as many cosmetic upgrades as the 2Gs, but the 1G engines are much better. There are a few more mods you can try with the 1G engine. Get a new exhaust manifold. If you can find a 2G exhaust manny, that would be an ideal swap. The 1G mannys are more strictive and are known for cracking. Get a 2G MAS for your K&N filter. They allow for better air flow. An 2.5" upper intercooler pipe will help as well. Put a catch can on your PCV valve hose instead of having it route into your intake manny. Get a breather filter for your the breather hose going from your valve cover to your MAS to turbo tube. These mods will prevent your intercooler from building up an oily film and reducing your performance. If you really want a lot more boost, go for a "Big" 16G turbo. That can easily add another 20-50 bhp.
Hope that was helpful.