Is a 6v power adapter safe to use on four fans? Heres what I want to buy: Newegg.com - Rosewill RFA-120-K 120mm Case Fan Newegg.com - Link Depot 12" 3pin UV Power Supply Extension Cable Model POW-UV-12EXT 6V/1800mA AC-to-DC Power Adapter : Power Adapters | RadioShack.com Thanks a lot!