Ok, basically there are 2 types of Amiga monitors:
1) The 'normal' Amiga monitors which are well suited for older Amigas like A-500 and A-2000 without grafik card, which will always display a 50Hz ( PAL ) or 60Hz ( for NTSC ) picture.
2) The multisync monitors that will allow higher resolutions on AGA machines or machines with grafic card. These are good if you use an A-1200 or 4000 and can switch to higher frequencies if the Amiga is using a screenmode with higher frequency.
But you can even use a type 1) monitor with an A-1200 or 4000 if you are just playing games, because even AGA games will not use the higher screen resolutions and therefore the A-500 monitor will be ok. Only in case you want to play very new games with grafic card support, or if you are doing serious stuff with your Amiga, then you will need a multisync.
Ok, since I think you are planning to use the monitor for your CD-32, a 'normal' type 1) monitor will be enough. You can play every CD-32 game on it
I would suggest a C= 1084-S or a Philips CM-8833-II. These 2 have a very sharp display and stereo audio !
The 1084 ( without 'S') is the same as the 1084-S but is mono only. The Philips CM-8833 is also rather good, I think, but stay away from the CM-8802 as at least the one I had had a blurry picture.
If you want a multisync then I would look out for a C= 1960 or 1942 or a NEC multisync 3D. I think also the Microvitek 1438 is a multisync monitor and I have heard it should be quite good.
Hope this helps a bit