I had this same question and waited months to find a deal. Finally, Saltwateraquarium.com (they also ship within days versus weeks because they don't "drop ship" and have them in their warehouse) had a 5% store credit on all aquariums, including Red Sea, on cyber Monday. They also gave 5% rewards, so I received over $200 in store credit. I was able to turn around and use that credit within 24 hours to get other holiday deals on stuff like filter socks and test kits.
Unfortunately, the tank arrived chipped but their customer service was really good and they contacted Red Sea who shipped out a new tank (took weeks to get though).
My LFS said they could discount the tank $150 off from online retailers, but the 6% sale tax negates that.
Love the Reefer 450 by the way- plumbing is a dream!