Remember that when you are looking to get a better return on investment (ROI) for your direct marketing campaigns, that you need to increase returns AND decrease your expenses for maximum impact. Seems simple enough, but most folks fixate on getting better returns without looking at the expenses.
When examining your expenses, remember that almost every study that has been conducted on the effectiveness of direct marketing campaigns has showed us that the "creative" element of the campaign (i.e. design, print, etc) has less to do with its success then the proper targeting and pitch. However, how many of us get sucked into spending a majority of our budget on high dollar graphic designers and top end printing?
So here is my advice: unless your campaign absolutely needs a top dollar graphic designer and premium printing services, save your money and invest more time and energy into compiling your mailing list, analyzing the data in your database, and putting together your pitch.