Help Desk – Service Order Tracking

My company is a small time network VAR. Like any other service company we have tons of calls come in. I am looking for a service order tracking system that others find work well. On my wish list is Internet availability for techs and clients for entry and responce to service orders, ability for the tech to use a PDA and resync with the main data store, tracking of clients that have prepaid service, solutions database (gee no reinventing the wheel?) and management reports. I looked at Track-It but it seems that it is geared to a single client rather than a VAR servicing dozens or hundreds of clients. What works???