I have had excellent experiences with
MyTransferSource.com. Good prices, quick turnaround, quality transfers, and superb customer service.
Just curious as to why you are planning to outsource, though. I outsource because I'm just experimenting at this point. However, if it were the core of my business, even though it does have its advantages, I would think that outsourcing would just be too much trouble. Have you looked into purchasing a printer and setup for sublimation?