They really do sound better, but this is a very good question (justifying a new receiver right away). You already have better audio as most DD on BD are running at cinema speed of 640 instead of DVD 448. Also, the "core" in DTS:HDMA is the true DTS 1.4Mb and not the 700K running on DVD.
You may also want to experiment with collapsed surround sent as uncompressed PCM2.0 and re-expended in the receiver to see if you get a better output from the lossless HD formats.
My personnal opinion would be to wait if you don't mind too much and get an even better deal later, or even go with a pre/pro (Outlat 997, for example) and use your current receiver as amplifier only.
