Need advice on receiver (and possibly sub woofer) to buy..

I am a novice about sound systems and need your help in finding a good receiver.

My current setup:
I have an ~12 yr. old Bose Accoustimass 5 system. As many would know, this one came with a passive sub-woofer and 5 cube speakers. My receiver is a Yamaha RX-V793 (again ~12 yrs. old) which has only Dolby Prologic decoding capability.

In this setup I have, connections go from the binding posts on the receiver to the sub-woofer. The sub-woofer separates the channels and transfers them to FL, FR, FC, RR and RL cubes.

I use a DVR for TV programming. Roku for recorded TV serials, PS3 to watch blu-ray, Wii for some games and HTPC to watch my videos & music. These are connected to a Samsung 61" DLP TV.

In the current configuration, all my devices (DVR, PS3, HTPC, Roku) are connected to the HDTV through HDMI cables. The TV is connected to receiver using RCA cables. I think this may not be the right way of connecting an audio system.

Long-term Plan:
I would like to gradually replace the audio equipment over a period of time. The receiver I plan to buy should lat me for the next 10 yrs. I am not an audiophile. I mainly use the receiver to watch action movies with earth-shaking sound. Another point is I am also pretty bad at balancing my speakers and would like some automated help, if possible.

Questions:
1. To resolve these issues (lack of new audio codecs for blu-ray, HDMI pass through etc.) I am in the market for new receiver. Can you gents suggest a decent (and relatively inexpensive) one? Since I am in TX, I don't need a receiver that would also serve as a room heater.
2. Can I replace the passive sub-woofer in my Bose Accoustimass system with a powered sub-woofer and then directly connect all (FR, FL, FC, RR, RL and powered-subwoofer) directly to the receiver? Will this damage the Accoustimass 5 cubes?

My guess is this probably would remove stress from the receiver and I could go for a receiver with a lower power consumption, but better capabilities.

Apologize for the long winding note, but would greatly appreciate any advice you can give me on make and model of receiver and also suggestions on sub-woofer, if you think it is needed for my setup.

Thanks..

Thanks jdsmoothie. I think I can spare around $450 for a receiver. Can you suggest other alternatives as well in Pioneer and Yamaha? Now that Thanksgiving is just round the corner, I may be able to get a good deal in a B&M store!!

Appreciate the advice. I finally wrestled with it for a while and placed the order for a Pioneer SC-1222-K (7.2-Channel Network Ready AV) Receiver. Got this for $600/- at Newegg, after discount. Awaiting its arrival and plan to connect everything through the new receiver (and of course planning to sell the Yamaha RX-V793)..