The inexpensive Toshiba DVD players have been audio favs in other corners of the internet. A couple of years ago a whole bunch of folks were actively modding them. The most basic (SD-4100) is $45 at Best Buy. It has a digital out. Folks like this player because of the decent audio dacs, which I presume you won't be using. Some Samsung models use the same electronics as the Toshibas, but look a little fancier and are still under $100. Generally more $$ just gets you fancier video features and maybe a prettier box.
I have an older 5 channel version of the Toshiba that I picked up at a pawn shop for $20. It sounds awfully good, but I prefer my old 1991 Philips and it's TDA1541A dac for audio. It also has a quieter transport than any newer player I've heard (below $1000) I'm sure a few mods would have it competing well with fancy stuff, but I don't feel the need to worry about it for DVD use.
The Toshibas are a very popular, so it isn't difficult to find them. As with all consumer electronics, reliability is an issue. But if it dies out of warranty, another isn't terribly expensive. I'd avoid the generic brands unless you want to buy three. Once you get to a quasi-name brand like Toshiba, the build quality is about as decent as you'll find until you spend multiple hundreds.
I also like the Sony refurbished site for cheap players, but I don't think you'll find a digital output.
Paul J.