i think if its a g reg its an ed model and the engine should be a d14 in which case an easy swap would be a d16a9 engine which was fitted to the crx 16i-16v non vtec which gave 130 bhp as standard and can be bought for peanuts. the d16 motor is used in the states but its the single cam 16v but all the bottom end parts are interchangeable which means you can buy steel cranks h beam rods forged pistons alloy flywheels and cheap turbo kits

you can fit a b16/18 vtec engine but at great expence in which case i would go and buy a vtec to start with.
vtec is good but can get boring after owning a turbo as i say its good and sounds wicked but you would want to turbo it after a while.

i have a 16-16 crx at the moment and its as fast as vtec because its lighter but everyone wants a vtec.