I think EAC is capable of ripping hdcds, as far as the extra "quality" you get from them:
I seriously doubt that this would be worth the effort. Having read the technical infos about HDCD which are publicly available (the AES paper) I currently believe HDCD to be just a technology with quite low benefit compared to plain noise shaping. It's just a thing to make a bit money.
They are claiming 20 bits dynamic resolution. This is actually 16+1+3 bits where approximately one bit is gained via this peak compression and three bits are gained via noise shaping. While playing an HDCD signal WITHOUT a special decoder you'll roughly experience the same signal to noise ratio compared to the output of an HDCD decoder. The peak decompression mechanism which is part of an HDCD decoder is fairly simple, but it won't increase the signal to noise ratio because most of the signal (except the peaks) will get attenuated by 6 dB.
IMHO the best thing would be to leave the format (44 kHz, 16 bit) the way it is. Even without a special wink.gif decoder you will still benefit from the noise shaping part and get roughly 19 bits dynamic resolution.
1) dithering + noise shaping
2) peak compression (kind of a reversible dynamic compressor)
3) hiding commands in some least significant bits of the samples to tell an HDCD decoder which anti-alias lowpass filter it has to use for upsampling
...whereas most of the dynamic range "increase" comes from (1).
("increase" ? yes, it depends on how you measure it. If you perceptually weight the quantization noise the noise power will be lower compared to dithering without noise shaping)