Word of advice on upgraditis improvements

I currently have Sony 55" SXRD DLP (HDMI), Denon 2105 (85x7, non-HDMI), and the early 90's model Polk LS 90 towers, CS 350 center, and M3 surrounds; no sub at this time. I would like to move on up to separates, but not sure if I can swing the cost for the bigger boy toys with HDMI capabilities. My question is: Would I see and hear more improvement if I move to a receiver w/HDMI capability and decent power (Marantz 7002 or 8002 is something in mind) or move up to used separates here from an Agoner but only able to jump up to non-HDMI pre-pro and amp (Anthem AVM 30/A5 something in mind) and just run RCA interconnects and just plug and play HDMI straight from Blueray and Cable directly to monitor (with the option to upgrade AVM 30 to the 50 HDMI version at a later date). Any helpful advice would be greatly appreciated. If you would like to throw out some sub suggestions with any options, that would be helpful as well.

Thanks in advance,
Slitty