If I play Blu Rays with DTS HD sound via a 5.1 system that doesn't support it do I loose quality?

Welcome to the land of 'Home Cinema'. You are right in thinking that you will not be DTS-HD track but the 5.1 will be ample. I'm know to be very fussy but the 'system' you have is actually a great entry into H/C. To gain any benefit from DTS-HD you would want some high-end equipment first and a well calibrated (to the room) system. Your receiver also decodes DTS (as well as Dolby) tracks so you will be getting all the 'effects', just do take the time to position the speakers correctly, not only in actual position but think what you place them on, don't let them vibrate etc. When/if you feel like going further into quality sound here are some upgrade options: Use some better speakers. Richer have a good range of 'Bookshelf' speakers and 'Centres' (the one you listen too the most) and often some good deals. The great thing is you don't need to buy them all at once, start with a centre and work your way round. Get an 'Active' sub-woofer (ie one that has a built in amplifier, making sure it accepts speaker level input). This not only gives you a much better/stronger bass effects but takes some of the strain off of your main amp to deliver to the rest of the speakers :) Replace the receiver/amp with a decent unit. By this time DTS-HD receivers should be very affordable. You probably buy a 7.1 channel unit so now would be the time to buy a nice pair of 'Floorstanders' and some decent speaker cable. The nice bookshelf speakers you bought now get relegated to the side/rear channels and you have a good system, great for playing your music through as well. But some decent cables all round Enjoy. P.s. Do you realise the system you have purchased has a sound 'loop back' ie it will feed the sound FROM the tv into the amp/speakers if you connect with a HDMI cable for when watching terrestrial tv.

DTS Master HD is UNCOMPRESSED while DD5.1 is compressed. In some respects it "can" be better. But this means: * The Movie studio had to pay to do a decent sound mastering for the un-compressed track (and Hollywood is very cheap so only some major titles have better sound engineering). * You have to have speakers that can expose enough detail so you could hear the difference between the compressed and un-compressed track. To put a number on it - you need audiophile speakers starting about $600/speaker to be accurate enough. * You have to have decent amplification to drive the speakers. Hope this helps.