suggest an ogg encoding quality setting

I just got a hold of an album that I will not be able to live without. Its 320k mp3 right now. I know ogg sounds better, and if I enc to ogg I wont have to worry about DRM. Usually I just rip to 128k, but this album cannot be bought anywhere so I *really* want to preserve its quality.

My question is, what ogg rate sounds identical to 320k mp3. Also I am using CDex and I wonder if someone knows of some more actively developed software for this.

I have done some web searching and found that the 190's would be good for ogg, but it never hurts to ask I think.

Why not rip to flac for a backup copy? It decodes to be bitwise identical to the CD with a decent enough compression rate.

For ogg/vorbis, the hydrogenaudio wiki suggests -q 5 as the point of transparency if you're encoding from a CD - that's VBR with a target of around 160. They're using some special tweaked and tuned oggenc, so I don't know how well it applies to whatever version is in ports.
I use "-m 64 -M 350" with oggenc.

You should consider FLAC as Djn suggested. FLAC won't drop a single byte of audio data, so it sounds exactly the same as the CD.
Nothing you can store in can ever be better than what you have now. As Djn said, use flac if you're backing up a CD.

It sounds like you're not, though; all you have is the MP3s. If that is the case, back those up as the originals, because nothing else will ever be quite as good.

If you want ogg for listening to, that's a somewhat different question, because you'll be keeping the originals as backups. Unless you listen through an unusually good sound system, 350kbps MP3 is probably far better than you will be able to hear anyway. If you're using $5 headphones, you can probably shrink it to 100kbps (nominal; Ogg Vorbis usually involves variable bit-rate resolution) without any problem.
Honestly, 320k is way beyond the human hearing in quality loss. And additionally encoding compressed data only leads to more quality loss. Enocding to Vorbis will only get you better quality (not at q5, in my opinion) if you do so from a source without lossy compression, such as .wav or .flac.

BTW, I encode my music in q6.
As mentioned, the oggenc the hydrogenaudio people use has had a lot of tuning beyond the version we've got in ports - so it makes sense to use a higher quality level on the stock one, indeed.