UCLA PO's
cdw To purchase with a PO, get a quote with shipping from the vendor, and email that to a purchasing officer (Mary Metz as of 2013). Email the purchasing officer a copy of the packing slip when the item arrives. If it's electronic delivery, email the confirmation.
CDW-G is a preferred vendor and as of 2013 has reasonably competitive prices. Get and education/government account to get the discounts (or use Paul's account).
Dell offers excellent prices for UCLA purchases. You will need to log on to a Dell premier account (ask Paul) to get prices and quotes. This is different to the education accounts. The IT help desk can also get a quote. Note that KST will fulfill the Dell orders, which is why some Dell orders will have emails come from KST.
Vendors that don't take PO's
newegg usually has the latest products at excellent prices, but since 2012-2013 has been cluttered with lots of non-computing, consumer items. Good return policies.