According to the gentoo wiki http://en.gentoo-wiki.com/wiki/LIRC
the LIRC_DEVICES variable currently only supports one flag (which may be why it was commented out in the stock make.conf that was on my system since it had 2 entries). The solution given there is to use "all" if you need to support more than one type of hardware, which failed to emerge on my system, perhaps it could be worked out but thats not what I needed.
The 8.4 ebuild had a warning when you selected more than 1 device.
ewarn "When selecting multiple devices for lirc to be supported,"
ewarn "it can not be garanteed that the drivers play nice together."
The 8.4a ebuild seems to have removed this warning.
Perhaps this issue will sort itself out upstream.
While I could request the flag be set to hauppage the average user would probably prefer it be set to mceusb2, which is supported on XBMC out of the box. The Microsoft MCE remotes are cheap/plentiful enough so I could buy one(I'd need 2, once I convert my other mythbuntu/XBMC box to Sabayon), but in the mean time I'll just emerge with the proper use flag for my system.