Monitor/headphone issue

I'm hoping someone can point me towards what to buy to solve this problem.

For the longest time I've been using a mixing board as gain control and a headphone switch for my monitors. Here's the rough layout:

I've been aware using a mixing board for this small task is stupid (and a waste of desk space) for a while but I didn't know what to replace it with. The board's slowly dying now though so I need to figure out what to replace it with. Here's what I've thought so far:

• I could plug the Delta 66 sound card directly into the monitors, but then how do I switch to the headphones? I hate dicking around in software to change volume and settings every time I want to do something.
• I thought a headphone amp like the Behringer HA400 might be what I was looking for but I'd have to feed my sound card output into one of those headphone inputs and that seems sorta gross. Also I don't need the two extra outputs and would like a mute switch for the monitors.

Aaaand that's about it. Digging through Behringer's product list hasn't helped much. Basically I need two 1/4" or XLR inputs & outputs, two volume dials and a mute button in a wee little package.