I find the RS-1 and HF-2 to be quite different. For me, listening to the RS-1 is akin to having hot needles repeatedly stuck into my ear drums. The HF-2 is much more like the old HP-1000 series. It's very balanced and only slightly warm. I prefer it to the new PS-1000, which to me has way too much bass. At the HF-2's price, it's quite a deal IMO.
However, I did get an HD800 too.