By my calculations, ZC pistons in a D16A6 should yield 10.8:1 compression. You should be able to pick up a set new with rings for about $200 or less, used for even less than that. It's up to you. If you're staying all-motor, then OEM cast pistons won't be bad at all. Boost, you'll want to get forged pistons, but raising compression isn't something you usually want to do before boosting, so I assume you're staying all-motor. It's up to you to decide if you want to pay twice as much for 0.2:1 more compression.