George:
I'd forget the VGA input and stick with one of the component inputs (#1 or #2). I've tried various ways to use the VGA input and bypass the internal scaler, although I'll admit I've not thought of a DVI to VGA conversion. I've also tried many different DVD players with the 9000.
Bottom line, the internal scaler is pretty good on the Sharp 9000. There are just too many other variables when adding an outboard scaler (I've tried Focus Enhancments, Lumagen and Iscan Pro). Sometimes the picture is better, most times not and a lot more complicated to set up, operate and enjoy on a day to day basis.
My advice is to find a used Panasonic RP82, XP30/XP50 or a Denon 1600 and run in progressive mode into the 9000. My family, myself and guests are continually amazed at the quality of DVD production with this setup. Likewise, HDTV (Cox cable with Motorol 5100 decoder) is absolutely stunning thru the component input on the Sharp 9000. Yes, there is a little edge enhancement that is accentuated by the Sharps internal scaler, but on good material and with proper sharpness adjustment you will hardly ever notice it.
I've had my 9000 for > 1.5 years now and have had a couple of HD2 chip machines in my system as well (including the Sharp 10000). The Sharp 9000 is bettered some by the newer units, but most non AVS types wouldn't notice the difference without a direct comparison. I spent my projector upgrade money on decorating, chairs, paint and accessories.
My advice is don't sweat the small stuff, enjoy the Sharp 9000 out of the box with a good progressive scan DVD player and HDTV decoder.
BTW, the single biggest improvement I've made with my Sharp 9000 was replacing the bulb at 900 hours with a new one. This totally blew away any other changes that I had made to my system. I had not noticed the subtle dimming of the bulb over time. I will replace my next bulb sooner.
Good luck.
mooneycj