Seagate is giving away AUD $30 / NZD $34 cash back when you purchase at least 2 eligible Seagate NAS HDDs and register at the site linked.
AUD $15 / NZD $17 cash back for any additional Seagate eligible NAS HDD up to 8.
Up to $110 Cash Back when you purchase an eligible NAS with 2 eligible Seagate NAS HDDs.
PROMOTION LIMITATIONS: The promotion limit is up to 1000 drives claimed. Once this limit has been reached, the promotion will end, even if it is before 1st April 2016. Eligible products are sold via authorized ANZ distributors. Preferred partners are shown at the bottom of the page but I'm assuming there are many more authorised ANZ distributors.
Seagate Eligible Products:
NAS HDD 2TB (ST2000VN000)
NAS HDD 3TB (ST3000VN000)
NAS HDD 4TB (ST4000VN000)
NAS HDD 6TB (ST6000VN021)
NAS HDD 8TB (ST8000VN002)
NAS HDD 2TB +Rescue plan (ST2000VN001)
NAS HDD 4TB +Rescue plan (ST4000VN003)
NAS HDD 6TB +Rescue plan (ST6000VN0031)
NAS HDD 8TB +Rescue plan (ST80000VN0021)
Seagate NAS Diskless Eligible Products:
2-bay model STCT300 $20.00
4-bay model STCT300 $30.00
QNAP Eligible Products:
2-bay models TS-231,TS-251+ $30.00
4-bay models TS-431,TS-451+ $40.00
5-bay model TS-563 $50.00
6-bay model TS-653A $60.00
8-bay model TS-853A $80.00
Synology Eligible Products:
2-bay model DS716+ $20.00
4-bay model DS415+ $30.00
5-bay model DS1515+ $40.00
8-bay model DS1815+ $50.00
NOTE:Synology NAS claims are limited to 20 per each model. Once the claims for the model has reached the limit, only the cash back for the NAS HDDs will be processed.
D-Link Eligible Products:
2-bay models DNS-320, DNS-327 $30.00
4-bay models DNS-340, DNS-345 $40.00
Full T&Cs here: http://seagatepromo.com.au/nas-hdd/terms-conditions/
Total discount works out better if you buy the smaller drives. Cheapest price I've found for the Seagate ST2000VN000 2TB is $122 each, so with the cash back they're $107 each. Also found the Dlink DNS-320L for $124 which comes down to $94 if purchased with 2 eligible drives. The lot for $308 after cash back seems alright.