IMac PPC :: Choosing Bit Depth While Recording Audio?

Do you know of any simple audio recording app (ie: not a monster audio suite) which takes low CPU usage, and lets you choose the internal bit depth using for audio sampling (ie: sample at PCM16, at PCM24,...)  ?  

Now, in case you need it, the long version of the question: 

I'm digitizing my huge collection of audio tapes, with my G5 iMac (OSX 10.4). The quality of the recordings is somewhat low, so I don't need a high-end audio card, and I believe the builtin audio card of this G5 is more than adequate for this task (Burr Brown PCM3052 with support for PCM16, PCM24, and AC3 16). 

I've done my first tests with the just-released new version of Audacity (2.0.0), which is compatible with 10.4 and higher, so I'm very happy to be able to install a brand-new application in 10.4. 

Audacity works fine, but has a couple of issues: 

First, you can choose the audio track bit depth, but not the internal bit depth at which you're sampling. In other words, I'd expect to use some selector to choose from PCM16 or PCM24 recording, which is what this iMac seems to support. However, I can only choose the storage bit depth, not the sampling bit depth. I suppose Audacity is recording at PCM24, but I've no way to test this. 

Second, it takes about 40% CPU usage while recording (yes, I disabled the realtime graphics update of Audacity... if I don't disable it, usage becomes 60% or higher). 

I tried Audio Hijack Pro (well, the last version supporting 10.4), and it won't let me choose the sampling depth either. 

Info:
iMac, Mac OS X (10.4.11)