Large Scale, Professional, Mail Merge Apps?

xtermz asks: "I recently began working for a mid-large scale print house. We do everything from printing of sales fliers to invoices for some fortune 500 companies. For doing these invoices, we use something called JetLetter which is basically a mail merge program on crack. It lets your create a template, pull from a database and send a PCL stream to your desired printer type. The problem with this program is that it is designed only to pull from flat text files, or antiquated .dbf files. It can't support SQL Server, XML, or anything made after say...1992 (even though they have a 'JetLetter 2000' version, which is basically the same DOS based app with a 'Windows' interface). If you try doing a search for 'mail merge', your likely to get back a couple thousand hits for MS Word. Talking to my co-workers, JetLetter seems to be the only solution which suits our needs." Many people seem to think that to do "mail-merges" you need a word-processor. Not so. A mail-merge is simply applying a subset of data over a text template. Looking at the problem this way, can any of you offer suggestions to a solution that xtermz might be able to use to replace (or supplement) JetLetter?