An interesting but tough question to answer! It depends a lot on the quality of the new DAC and its jitter immunity vs the quality of the DDE 3.0.
I can supply some anecdotal evidence. Last year I set up an (relatively!) inexpensive second CD front end to experiment with HDCD decoding, which my existing Wadia front end doesn't support. I already had a DTI32 PRO, and I acquired a used AA DDS PRO transport (sounds great - lousy display!) and a used DDE 3.0. I2S connections ran between the transport to the DTI and the DTI to the DDE.
On HDCD's the sound could be spectacular, but was often kind of grainy with a tubby bottom, depending on the HDCD. The same HDCDs, played undecoded through my Wadia 25, sounded great.
On ordinary CD's the DDE3.0 was just OK - quite uninvolving. The same CD played back on the Wadia front end could be riveting. Note that I played back CDs through the DDE using the 20 bit dither seting on the DTI PRO 32.
BTW, the DTI Pro 32 had the Advanced Dither chip, and the DDE3.0 had the remote option. Both used AA Power Station 3's instead of the Power Staion 4 wall warts supplied with the products (replacing the PS4 with a PS3 on the DDE3.0 made a significant impovement in its sound - but not enough).
I decided to try another DAC. I bought a Parasound DAC 2000 off Audiogon at a good price. This HDCD DAC has a good reputation and I figured I could easily resell it if it didn't pan out.
I hooked up the DAC 2000 to the DTI 32 Pro using AT&T glass fiber (SPDIF of course). The DDS Pro - DTI 32 Pro link remained I2S. The DDS Pro - DTI 32 Pro - DAC 2000 combination totally outperformed the same combination with the DDE3.0 in lieu of the Parasound DAC. Now most HDCDs sound excellent, and the tubby bottom is completely gone.
So the moral of the story - arrange to try out the new DAC at home, using a good quality interconnect. Let your ears make the decision.
I haven't listened to the Alpha, so I can't make any relevant comments on this DAC.
Good luck, and welcome to the exciting world of audio experimentation! Remeber to protect your wallet!