I think RVW's symphonies are seriously underrated. I don't mean this to take away from Sibelius, Mahler, or Bruckner; but I think RVW's symphonies rank right alongside of them. His 9th, in particular, fascinates me. The only ones that attain "merely good" status for me are his 7th and 8th.
I like Vernon Handley's cycle. Slatkin's with the Philharmonia is good, but I would have preferred that he would have recorded it with the SLSO instead. (What can I say, it's my hometown bias showing, although I think critic David Hurwitz made a similar case in Fanfare, several years ago.)
Great stuff!