Paul:
I've had good luck with the metallic frames from pictureframes.com with their acrylic glass or just the frames. These run about $35 each for 16 x 20. Your requested size would be larger and even more expensive, but this is a one-time cost and you can use them over and over as you change your images. I use mattes from goldenstateart.com. Gpldenstate has cut or blank mattes. Cut mattes are handy, blanks are more versatile. They offer free shipping on, which can be expensive, on a number of common items, if purchased in quantity lots.
You can hang the frames from pictureframes.com a number of ways. They give you connectors and a wire to hang them in a traditional manner. I almost never use this. In my living room I use velcro command strips. In my office/lightroom, where I display only black and white, I use a rail with that supports the wire brackets, slightly bent - without the wire, and at my work I use push pins. With the acrylic glass, these frames are quite light and the metal frame has a channel that fits a push pin well. I've come to think that this is the best way to hang them, though at my house I have skim-coat plaster walls and they don't take push pins well.