Good plan I think for 340SE across the front and moving the 170s to surrounds (not 170SE, actual original 170s). My Sierra1s are my LRC and my 170SEs are surrounds in my bedroom 5.2 setup. Always wanted to try the 340SE but never did. That avr should do it well enough, good that its out of the way as long as you're going to work into its capabilities down the line....otherwise a bit of a mismatch with a pair of 170s