Do you have local auction/sale websites in your area?
I got a decent AV amplifier just on a second hand goods auction site called
Gumtree, and it has HDMI inputs. I got it for $120 Australian dollars, and it works very well. The one I got was
Onkyo TX-SR252. That one is 5.1 channel.
Maybe keep your eye on auction sites etc. and see if you can get a better AV receiver/amplifier. Hopefully you will be lucky like me and get a nice one. I am sure you are probably doing that already though.
I see your amplifier has a digital optical (Toslink/SPDIF) input. Are you using that for anything?
If you are already using it, you can get things like this also, although it begins to get a bit messy perhaps.
Toslink Selector Switch. You would need a soundcard with a digital optical output to use that. Also your money may be better spent just getting a newer AV amplifier.
My brain begins to hurt with too many ideas and possibilities.
{GoofyOne's 2c worth}