EDTV is 480p. I assume that your EDTV set has component video, possibly DVI, and maybe even HDMI. Any of these ports will give you a better picture than the RF that most people use to connect their digital converters to their TV sets.
For this reason, I recommend a digital tuner or an ATSC-compatible DVR rather than a digital converter. The ChannelMaster CM7000 PAL is my preferred choice. The newer ChannelMaster CM-7400 DVR has many more features. The downside to a DVR is the it costs at least $300 compared to about $50 or less for a converter. Also, as part of the Nation's digital changeover, every household is entitled to a Federal subsidy for two digital converters. This subsidy covers the cost of most converters making the less expensive models free to you.
In my experience, the single greatest improvement that digital broadcasts bring to your TV picture is the elimination of multi-path signals and "snow." Whether you have a tuner or converter, you will experience these benefits of digital OTA broadcasts.
You have your reasons for wanting to stick with your EDTV. However, that set should be getting long in the tooth about now. HDTV sets with 1080p flat panel displays are selling for just a few hundred dollars. Rather than worrying about which converter to buy or applying for the convert subsidy, you can just screw your antenna cable to the RF port of a new HDTV and enjoy your local ATSC broadcasts in all their HD glory [if the programs are broadcast in HD].