You may feel the green is too dark, but to be sure we're talking about the same color, Avon Green is nowhere near a Hunter Green. It is the grey green below between your other colors, blond wood, and barely beige.

Avon Green (HC126) and Hunter Green (2041-10) share similar blue grey hues, but Hunter Green is much more saturated.

You might want to consider Garden Path (466, top) or Antique Jade (465). Either will go well with your palette.

EAM44, I love Garden Path! I'm not sure I see yellow working well with the other two colors.

Yellow isn't outdated at all. In fact Benjamin Moore has chosen Lemon Sorbet as its Color of the Year for 2013.

{{!gwi}}

I'm not sure it's the best choice with your other colors though. Maybe it depends on where those beige walls are exactly in relation to where you think you'd like the yellow. This one is Yellow Iris.

I like the greens above too.

I think adding an additional color like yellow might look a little complicated - too many colors in one space. I would even remove the blonde wood, and replace it with a white, like white opulence, for example. The Garden Path palette would look as follows:

And Antique Jade:

Fabulous suggestions! Thank you so much! It did cross my mind to simply lighten up the green but I had no idea what the right color would be there. I've been testing yellows in there and finding the bright clear ones are way too much and the muddy ones clash with my existing warm beige. Antique Jade would be very pretty.
The Blond Wood and Avon Green are both on two story vaulted walls that I'm not prepared to deal with right now so that has to stay.

Thank you all so much! Excellent suggestions! I had thought about just going lighter on the green but wasn't sure where to go with that. I've been testing yellows and they aren't working at all. I'm finding that there are joys and pitfalls to having a very open floor plan. :)