I wouldn't return the receiver, it is working fine apart from the USB tuner I trust? There is no guarantee that another receiver will work with that USB tuner.
The Sundtek tuners are very good. They work in a sort of "separate environment", independent of receiver's drivers/kernel. One of the receiver I have won't function with USB tuners, the Sundtek works. One some of my other receivers, a USB tuner used to work, they chanegd the drivers and the USB tuner no longer works. But the Sundtek still works I'm led to believe. Sundtek are usually very quick at fixing things and provide good after sales support including through skype.
It is your money at the end of the day. Also depends on what your retailer is prepared/obliged to do. If he/she offers you a refund for the USB tuner and you buy the Sundtek, that would be a good outcome IMO.