There's really no converter to 'make' a receiver support hdmi 1.4. There are workarounds to get things working, but I believe you're probably better off just replacing the receiver. 3d-ready receivers can be had for under $200 (sony vsx-520-k, onkyo tx-sr308 for a couple starting examples I'm aware of - there are probably several more).
Or you could simply use an hdmi switch and connect to your amp with other types of audio cables - for example optical output from your PS3, spdif from your htpc if you have one, that kind of thing. It's a bit more of a pain to hook up, switching gets more complicated, and the audio modes aren't quite as nice, but it would be a solution.