PC/Unix platform for GRASS?

Folks,
  I'm fixing to order a PC/Unix platform to which to port our GRASS-based
applications. To save me time and anxiety, could someone advise me

  1) What Unix product(s) and versions has GRASS been ported to?
  2) What hardware configuration constraints should I be aware of?

Thanks!
  Steve Frysinger
  AT&T Bell Laboratories
  TEL: 908/949-7596
  FAX: 908/949-6029
  NET: spf@hoqaa.att.com
  SLO: Crawfords Corner Road
       Holmdel, NJ 07733