Upgrading from your old receiver to a new one will give you HDMI, which will allow you to pass through the new lossless audio soundtracks (Dolby TrueHD and DTS Master Audio) from your Blu-ray player.
Using any other form of digital cables will not give you that lossless sound (which is phenomenal, btw). The only other way you can get Lossless audio from your Blu-ray player to your AVR is if BOTH the blu-ray player AND your AVR have 6 channel analog audio out (mine did from about 7-8 years ago, so there's hope), but the downside is, of course, once connected properly, you will have a rat's nest of cables behind your gear.
