Hi,
I actually have the Philips HD1500 wireless headphones downstairs hooked upto my DVD player and i would love a 2nd pair for upstairs (hooked upto a mac mini via an M-Audio Transit) but they are impossible to buy now.
I tried the pioneer se-dir800c and they sound ok, but not a patch on the Philips and i think the headphones are the problem, because when you plug other headphones into it, the sound improves.
So, i have decided on an external dolby headphone adapter and go wired upstairs.
I bought the Creative HQ2300D from ebay about 2 months ago (£25 ish delivered, refurb from Creative) and it sounds pretty darn good. The sound with movies is excellent. Its ok with music but not amazing. If you upgrade the headphones the sound is even better, I have 2 pair of wired headphones, Sennheiser HD 205 (£30 from currys) and a pair of Goldring DR150. The creative decoder sounds better with the Sennhiesers (most likely the Goldring need a good amp to perform well).
I have ordered a JVC SU-DH1, which is an external; decoder which runs on 2 AA batteries and is supposed to be the best one you can buy (not like there is much of a choice) but i got it for £60 off ebay delivered from the US (it should arrive here sometime next week).
I tried some friends headphones which are 5.1 and have lots of speakers and they suck to be honest.
I have tried most wireless surround headphones and the best ones are Sony (VPT) and Dolby Headphones. Dolby Headphone is by far the best. Steer clear of anything with SRS on it and anything with lots of speakers in the headphones.
Dolby Headphone rules!
Hope this is useful!