The sound experience between headphones and a HT system is going to be very different.
You could plug headphones into a receiver, but there are some things to keep in mind...
(I'm not a big headphone guy so I'm going to miss some stuff too)
Wireless headphones are not going to be as good as wired ones. If these are for watching a movie, could you just have a long cord between you and the receiver?
You're not really going to get a "surround" effect in most cases. You'll get a stereo downmix of 5.1 sources for most receivers. If your equipment has Dolby Headphone
http://www.dolby.com/consumer/technology/headphone.html, you'll be able to get Dolby's attempt at 5.1 through stereo headphones.
I'm not really sure which receivers come with that and which don't. I have it on my pre-pro, but it wasn't really a feature I cared about. It looks like some lower end HK models have it. I don't know if this should be a big thing to look for though... I wasn't blown away by dolby headphone when I tried it out vs. stereo.
What's your budget?
Does your wife not want the HT system due to aesthetics or other reasons?
EDIT: Yeah Muadib, I thought about mentioning 5.1 headphones (wired or otherwise), but I don't know if there are any really good wireless sets... and for the 5.1 wired ones, I'm not sure what connection types they all have. Are there some with DD/DTS decoders with digital inputs, or would he need to buy a receiver with 5.1 pre-outs?
Also I haven't heard much in the way of opinions for movies, but HeadFi seems to be quite anti-5.1 headphones in general.