I still use a 3440 - the 2340's bigger brother. It handles 12.5 inch NAB reels, and can be used with a DBX unit.

The record head is also the sync playback head, which makes it ideal for multi-track dubbing. You switch off 'record' on the tracks you want to listen to, and set the monitor to 'sync play'. It's a doddle!

There is also a separate playback head so that you can listen to what you have just recorded (not whilst dubbing, though!). This means you don't have to wait until after the recording is finished to realise you forgot to press 'record' on a particular track, and you can also adjust the level more accurately.

I haven't use the 2340, but I imagine it has a few features in common with the 3440.