If you can manage with the Hauppauge pre-learned IR codes, their blaster is okay. If not, good luck because it sucks at learning new codes.
An alternative: order a Windows Media Center remote and transceiver (HP OEM) on ebay, about $25 from China. Download the IR Server Suite from the MediaPortal forum. Teach it the codes and write a script for channel changes. Examples are provided with the software.
Should work with MediaPortal, NextPVR and with Media Center if you use the Colossus Bridge for DVBLink from 1geek1tool.