Just to elaborate a bit more.
With engines, its better (IMO) to do everything at once. You set a power goal, boost targets, driveability, and then put together a build. If you do it piecemeal, you end up doing a lot of repeat tuning and labor, and buying more parts. If you first decide to put in some 850 injectors, but then you want a bigger turbo, now you're buying 1000 injectors. And if you bought 1000 injectors the first time, you might have a rough idle or drivability problems. If you did forged pistons, but then decide to change cams and connecting rods, you're just repeating tearing the engine apart. Not to mention all the money on tunes!
However, with the suspension, it's a lot more subjective. I want it to be a little firmer, or it's too stiff over bumps. Its easy to go in and tweak, and you're not re-doing much (if anything). If you jump right in and get 5-way adjustable coilovers, with billet engine mounts, and MSI re-engineered everything, you could end up with a car that's not even fast...just undriveable. I'm pretty sure I don't know how to properly setup 5-way coilovers! And vibrations might break your back. Anyways, ease in with suspension.