I have a backend with two hauppage cards (150, 250). I just setup a frontend with no capture cards but would like to use the ir receiver from the
hauppage on the frontend, and use one of the remotes.

Is it possible to rewire the ir receive to use a DB9 serials input in order to
use it on the fronend?

Possibly, but I find it easier to have someone do it for me http://irblaster.info/

I have 3 of the IR receivers (not blasters). They work just fine with the silver dog-bone remotes.