I suppose if you want to save money you can always boost your SOHC now and tweak it as much as you want but, you will regret it in the future if you want more power by switching the whole engine for something better. All the time you spent into tweaking the SOHC to later do the same to the DOHC just seems a bit wastefull unless you've never done this stuff before and want to play with the SOHC. If thats the case then dont do this on your daily driver car.

Fastest SOHC d16y8 Civic I've seen was doing mid 12's street legal. You will get lower times with a DOHC tweaked in the same fashion as the SOHC. If mid 12's isnt what your looking for and you want to get lower times then yea do a swap to a better engine.