actually you don't need 3 computers to run X-plane on 3 screens as you would think, in fact the performance difference from 1920x1080 to 5760x1080 is negligible (either that or my PC is CPU bound bigtime) and that is with high performance settings, don't know about the licensing thing but unless those two new computers don't have a modern Gpu (Nvidia 600 series+ IDK as far as AMD is concerned (got 2 DOA GPU's in a row from them once so I pay no attention to them)) you should be fine running 3 displays on one computer