I have some Discover cash back that can reduce my upfront cost at Amazon on a Premiere 4 box. I already have a Premiere dual tuner on a month-month agreement. Can I buy @ Amazon the P4 & add the Lifetime Service to its purchase after from TiVo? I've read that there may be (by calling in) some current customer special pricing even less that the MSD $399 being currently listed - how true is this? Appreciate any feedback.