As you've probably noticed, DVD picture quality is probably outstanding on your new Plasma.
Even if an HDTV receiver is downconverting HDTV channels to EDTV, you will still get at least as good as DVD quality on your set (Standard D* channels are usually way overcompressed and are nowhere near DVD quality). Plus most HDTV channels are 16:9 widescreen, so you will have less stretching or worrying about bars on the side of that programming.
Also, HDTV receivers can get (for most people) HDTV locals OTA by just adding an antenna. You absolutely need to have an HDTV receiver to take advantage of what your plasma set can produce.
I have not been checking in the last month or 2 about deals / programming requirements, but I never heard of the requirement to subscribe to the $10/99 HD package (Isn't it free for the first 6 mo anyway?) All receivers (i.e. you buy one at BB or CC) added to an account just require a 1 year commitment to TC basic programming.
That said, The DRD486 is a SD receiver with Component out (But I'm not sure if it is still sold or not), and of course you should be able to run your current receiver through the VCR's composite inputs if you want to save up for an HDTV receiver.