I see not written in the post though
Extra 5% off orders over $999 with code HOLIDAYPC
Extra 10% off orders over $1399 with code HOLIDAYPC10
Well that's because it won't apply for items under $999.
The coupon doesn't work for items that are already discounted, if the original price and the price to buy it is over a thousand the coupon would work.
But yes buying two such laptops might do the trick.