OP needs to come back with more information (budget, what is to be used for)
i wager that any modern computer (past 5 years) can run dual screen, multi-task (well, at least 4-8GB of RAM) to use chrome+word+pdf
different story if you want to dual screen 4K @120p or triple screen, run photoshop/video editing software (likely want a powerful GPU) at a decent pace etc
for that purchase, $500-1000 is considered "low" budget for those requirements
prebuilt with warranty or willing to DIY (cheaper)?