I assume your talking about a stand alone dvd set top player. A player that only plays +R would be a strange one, since -R has a higher compatability 93% compared to +R 87%. Dual layer are here and some older players have trouble with layer breaks. I have found it to be more of a burning app problem Nero 6 & 7. There are high defination upconverting Dvi-D,Dvd-I, and Hdmi. True digital to digital in video, but came out as a form of digital rights management. I had a Samsung HD841 upconverting Dvi player. My opinion after four units repaired and new ones a piece O junk. Replaced with a Sony Hdmi upconverting seems to be ok so far.
I would look for one local with a 30 day return policy like BB. I would buy one with the RBG Red, Blue, Green monster cable type hook up. These are being phased out for copy protection. My Sony and Samsung had both. I now use RBG on Sony and have no problems, The Samsung I ran Dvi and nothing but problems. Then burn +R, -R and try Dual layers if you have a dual layer burner and see the results, remember the 30 day return policy.
A friend has a five year old Pioneer that will play -R,+R,+RW, and +R-DL with bit rate set to Dvd-Rom. My 4 year old Jvc plays -R,+R and +R-DL with bit rate set to Dvd-Rom. My new Sony plays -R,+R and +R-DL with bit rate set to Dvd-Rom, and the Nero disc with the layer break problem that hang up the older players.
Nero 5,6,and7 have worked fine on single layer burned dvd video file mode. Dual layer another story the best I found is ImgBurn or his older program, Iso read Iso write on Verbatim + R-DL with bit rate changed to dvd-rom. I haven't found a player yet that won't play this disc!
Remember to buy good blank dvd media that seems to cause most people all the problems.