amps dont have blu ray input.so if a seperate blu ray player plays the blu rays

Boy, you sound totally confused. Amps never have any inputs but preamp inputs, they are not designed to be used with audio playback sources, just preamps or receiver's with preamp outputs.

Second, if you want to watch blurays or DVDs, you have to use a player that can play that media and connect it to the preamp or receiver with either a HDMI cable or component cables.

Third, the Onkyo TX-NR609 and Pioneer VSX-921 have nothing to do with a bluray players performance. You need to find a review for the Bluray player you intend to use with those receivers.

Forth, as I said above, to play Blurays, you must use a player designed to play that media and either use the HDMI output or the component video cable outputs. The USB input on the Bluray players can be used to play a flashdrive with photos and music and some players offer video playback from a flashdrive from SD or even HD video files depending on the Bluray player.The USB port is not a video output for Bluray playback though.

Honestly, seeing your very confused about home theater components in general, you may be better off with an all in one system where the main control module is your receiver and Bluray player and uses speakers and a subwoofer designed for it. They are usually pretty cheap and Best Buy, HH Greg, Walmart and the like carry many different makes and models.

Good luck in getting set up.

If you connect the player to the receiver via analog cables (separate cable for each channel) and directly to the TV via whichever connection you prefer, then you could argue that nothing the AVR is doing is "about" blu ray, It's just playing back the analog sound it is being fed. THe player is decoding the Dolby or DTS stream and converting the resulting PCM into analog audio using the player's internal chips.

But if you connect the player to the receiver via HDMI (or use optical or coax digital connections for the sound) then the player simply streams the bits (not analog sound) to the receiver. The receiver then decodes the data, if it's dolby or dts, and converts the resulting PCM into analog sound with its own DACs. Then the receiver is performing functions that are relevant to blu ray. Not to mention however it may massage (or mangle) the video part of the data if it's not just passing it through unmolested.