HP might recommend that for the hotter processors but the load that current builds put on the power supplies can be quite a bit lower than in the old days. High end video cards and current SSDs draw so much less power..... and you are moving out those Reds over to another power supply.
I would encourage you to not go after the 1100W one..... eBay now is about $100.00 USD buy it now with free shipping for the 850W one. The 1100W is about 225-250 USD instead, and you don't need it.