Personally the 605 is a good receiver. You are getting HD sound and 1.3a HDMI. I would begin to invest in some entry level speakers instead of a new receiver. The Polk Direct store on Ebay is a really cost effective way to get an upgrade in your speaker dept. Here is a link to a 6750 Set that retails for 599 and is 99 bucks right now.
http://cgi.ebay.com/RM6750-Home-Thea...4.c0.m14.l1262