I've hacked together a Xft-enabled Phoenix build from a nightly Mozilla build and a nightly Phoenix build; you can download it here. It seems to run well under Debian unstable; it should also run OK in Red Hat 8.0 and Mandrake 9.
If you want to roll your own, see the unofficial Phoenix FAQ for details. That site also has extensions and themes that work with Phoenix; I'm enjoying the Qute theme, myself.