If you want to cover your bases, it might be prudent of you to invest in a receiver that will decode the new advanced audio codecs, however it is not necessary with the players that you currently have. Theoretically it should sound the exact same regardless if the player or the receiver does the...
While the sound quality in theory should be exactly the same, not all stand alone players might be capable of sending the LPCM signal (internal decoding on the player) for both TrueHD and DTS-HDMA, so it would be nice to have a receiver that is capable of doing the decoding.