Yeah the USB-UIRT is the perfect device for what you are after. I love mine. I use my tivo remote to control SageTV. As for IR blasting I haven't really set mine up yet because I so rarely use my digital cable box for recording. I set set up the ChannelChange Plugin that is used by Girder. It worked great. I just unistalled it since I don't really need IR transmit yet. Once my new HTPC is built next to my TV, I'll setup Girder agian.
If you want some help with setting up girder this
post/thread has a little tutorial on setting up the channelchange plugin. Also lot's of people in that thead and many other would probably be glad to help if you ask.
But it, you'll love it.
Michael