I checked out
eBay Australia and **** shits expensive over there. To get an xfl 15 in the states will cost ya 220 but 350 in Australia.
On my youtube channel I also have a video of a single 15 xfl I did in a Bonneville trunk. The truck is louder but not by much. So I'm sure it would be pretty nasty in your hatchback.
The xfl is rated at 1000 wrms so your amp would be totally fine for it. They can take 2k easily but 1k will still do you well. How much would it set ya back for 2 sundown sa-12's? For your power and plenty of space for 2 12's the sa's should get ya louder than the 1 15 xfl.