I'm personally using a recently purchased Toshiba SD-V592, and am generally pleased. while it can provide a variety of progressive & interlaces signal modes, 1080i seems to give the best PQ over 720P.
I can't provide more than a semi-subjective assessment as I don't own all the measurement equipment/time/inclination to do a comparison... I'd suggest you visit www.hometheaterhifi.com, www.theprojectorpeople.com,
or even eopinion.com to get convenient user/tester information.
So, after many, many hours & days of both online research & shopping/demos, I settled on this unit for affordability & availability reasons. There's simply too many to choose from nowadays, but you can narrow down the choices based on simple factors such as signal compatibility, connector outputs, and what you intend to use it for.
I playing with all-too-many combinations of signal types, cabling, & equip't settings. my experience (and equipment list) bears that the AE700 clearly delivers the best overall PQ via HD 1080i thru the DVI port from a Dish mdl 811 HD rcvr. Next best signal quality (practically imperceptable degradation) was HD via the component connections, also 1080i from this HD rcvr.
Next came the DVD. Since the SD-V592 provides both DVI & component outputs, there was a choice. I optimized PQ based on my equipment list, so the DVD drives the AE700 component input.
As expected, DVD PQ is phenomenal relative to 480i NTSC, but nothing touches HD!