need advice on a new 5.1 or 6.1 receiver

i'm new here and doing a little research on receivers so i can replace my old kenwood 5.1 receiver. here's my current setup:

kenwood vr-209 receiver(soon to be replaced)
frontL/R - pioneer S-H351F-K
center - sony SS-CN495H
rear L/R - sony SS-MB150H
sub - sony SA-WM40

and here's the catch, i'm going to be limited to the receiver selection at best buy(due to the gift card being used for the purchase) and a max of around $400.
i've actually been very happy with the output and sound quality of my kenwood receiver with my speaker setup, but i'm giving it to my parents along with a new speaker set as an excuse for an upgrade. i'm definitely going for DD/DTS in either 5.1 or 6.1.
also, if i upgrade to a 6.1, i'll need a rear center speaker, was thinking about getting another sony center channel to match my existing cc/surrounds.

any advice would be greatly appreciated. thx!