Low gain dac!

If you want to keep all of your gear, then try reducing the signal level between your DAC and preamp by using an autoformer with a fixed attenuation.  Technically speaking (and in practice), an autoformer will sound much better than reducing the signal level by means of any type of resistive attenuation.  In fact, it may actually improve the sound overall (making it more detailed and dynamic).

Contact Dave Slagle.  For $200, you can pick up a pair of AVC (autoformers) and have them wired for any fixed reduction you would like (let's say about -10dB to -15dB might be useful for your case).  If you are feeling ambitious, you can get these transformers wound with silver wire at a cost.  I believe the transformers are about 1.5" tall, 2.5" wide, and just over an 1" deep.  You will need a pair of these to fit.  If you're not experienced, have someone who is help you out with this DIY.  Ideally, you can get these to fit within your preamp chassis and wire up directly.  Otherwise, maybe you can fit them within your DAC's chassis.  If not, then this solution probably won't be convenient.  Good luck.

http://www.intactaudio.com/atten.html

@ggc, hello, sorry.  I think your best bet is to contact Slagle himself.  He has a variety of options that might work in your case.  He could probably help you figure out if his AVC would fit in place of your existing pot.  Another option is to bypass the existing pot in your preamp and use his EMIA passive remote AVC preamp as volume control for your preamp.  Only downside here is you will need an extra set of ICs.  I thought to do this (or at least have the flexibility to do this), but realized I like the AVC as its own standalone preamp better.  My EMIA preamp is wound in silver.