You don't wire the ANT chip to a sensor, but you can wire them both to the same Arduino. You shouldn't need both an ANT and XBee radio, unless you are building an ANt-to-XBee network bridge 
To interface to a PC, some dedicated USB receiver sticks are available (Garmin makes the 'official' one, but Sparkfun also has a version), or a second Arduino plugged into the PC can act as the receiver.
Sparkfun has modules using the older 'AP1' variants for about $25, about comparable with XBees. (They are hardwired in async. serial mode; the final library should support this mode too.) If you are making your own PCB it can be much cheaper (the IC itself is ~$3.50). If you go that route, I'd recommend using the newer 'AP2' series chip (nRF24AP2).
Anyone with advice / best-practices on a library design as described above?