If you go the N/A route, you either (1) won't need to get the pistons replaced, or (2) will buy a package which comes with pistons anyway, obviating the need for proactive replacement. For NOS, the cast pistons seem to stand up just fine to a small shot as long as it's properly tuned, so you'd only really want to replace if you start getting aggressive with the jetting. For S/C, you will be OK with the more conservative systems (DLM Level I, or Roe's stage 1) and if you go DLM level II Doug'll end up replacing your pistons anyway. I'd strongly recommend waiting until and IF you actually go a route which requires forged pistons before doing so.
That said, if you simply must have forged pistons, LPE, APEX, DLM, Cragin, Heffner, Valaya and numerous others all have operators standing by to swap you in a set, and maybe port your heads and replace your cam while they're at it...