I thought I should add my 2 cents, as I have been using an ADL Esprit since about a week now.
First a bit of history:
I recently replaced most of my T+A stereo system, and searched for a new pre-amp. When I first heard about the GT40, I have to say I had my doubts about it's sound quality. It simply seemed that there was "too much" in one package for that price. I instead bought a vintage pre-amp (Nakamichi CA-5) that has a highly praised phono stage. I mated the CA-5 with two Herron M-150 mono blocks, and Totem Mani-2 speakers until I rebuilt the T+A speakers (documented here). My turntable is a Project RM 5 with an Audio Technica AT120E/T. Not the fanciest cartridge, but very good sound for the price (my Shure V15 is on hold for a new stylus). Anyway, vinyls sounded great, the Nakamichi pre-amp really adds something special to the sound. I tried a Classé CP40 preamp as well, and also compared a couple of Musical Fidelity amps to my new setup--the Nakamichi with the Herrons sounded a great margin better (the Classé was especially disappointing).
OK, now let me get to the point. I have used the Esprit for digital playback, but also for a few tests to record vinyl (from the Nakamichi's tape out into the Esprit's line in). Setting up the Esprit was a snap, at least with Mac OS X and Linux (I don't really use Windows anymore). Just open your sound preferences and choose the ADL Esprit as your sound device for input and output.
Then I used Audacity for recording. You can easily adjust the levels in Audacity, so no going back and forth between sound preferences and audio app. And the results were truly great. I switched Audacity's settings to record in 24bit/96KHz, and it all worked without a glitch. I have not experienced any noise or static strangeness as some other people have reported about the GT40. If there is anything I could complain about, I would say that I do notice a very slight loss in treble, e.g. cymbals just sound more crisp on vinyl when the drummer swings the ride cymbal. But the difference is very minor, maybe even just psychosomatic.
The real fun for me was to discover that some of my vinyls that I also own as CDs sounded better than their CD counterparts. I assume that in the early days of CDs digitizing was not that great. For example, my Tower of Power "Urban Renewal" album sounds tremendously better on vinyl than on CD.
I should also mention that I used a Benchmark DAC1 for a little while before the ADL Esprit. The Benchmark is a great device, but I thought it was a bit overkill for me, and exchanged it for the Esprit (also due to the ADC feature). I could not make a direct A/B comparison, but, at least to my ears, I doubt that the Esprit sounds any worse than the Benchmark.
Back to the Esprit: I am very happy with it. I move it around in the house to use as a DAC, and have now started to digitize some old unique tapes of my bands. Otherwise I mostly use it as a DAC, fed to my preamp, mono-blocks, speakers, so I cannot say much about the headphone output. But it works great as a DAC, and I really appreciate the ADC feature for the times when I need it.
When it comes to your situation, I believe you are much better off sticking with the phono stage from your pre-amp (which I believe you already like very much), as opposed to finding a device like the GT40 with a built-in phono stage. Give the Esprit a try, I think you will not be disappointed. I got mine from musicdirect, which has a 30 day return policy, so in the worst case you would only loose the shipping costs.
'hope that helped,