Pioneer drives have scanning disabled in later Nero CD-DVD Speed versions because they are very unreliable for scanning. They are excellent burners though.
Samsung has some good burners and they can be made to scan by making a registry change (check in the Samsung Mini FAQ).
LiteOn DVD burners would be my favourite for DVD scanning and they burn some media well, but in my experience they are generally not up to the same burning standard as some competing brands.
LiteOn DVD burners are fairly poor CD burners in my experience and have very limited usefulness for CD scanning.
With only a single drive, an Optiarc 5200/7200 series might not be a bad choice, but I cannot guarantee the reliability of its DVD scanning feature.