Any reviews/input on Cary Audio Xciter DAC?

You are most welcome. I read the 6moons review of the Underwood-modified Music Hall 25.2 CDP and it sounds like a very nice unit. However, even if you paid an extra $100 to get the Burr-Brown op amp upgrade, I think the Cary would have the technology edge with its 32-bit DAC and collaboratively designed National Semiconductor output devices. Good luck with your decision! Either way you will enjoy your music more than ever.

Do you know if it accepts a 24/192 signal? Or something lower and so will always be upsampling?

Yes, the exciter accepts up to 24/192k.

http://www.caryaudio.com/products/xciter/XciterDAC.html

I have ordered the Cary Xciter DAC and will post some information on it after I receive it, and do some burn-in. I decided to just keep the Music Hall 25.2 as a transport and have the flexibility of an outboard DAC since there seems to be a lot of innovation/improvements going on with DACs these days. Also I like the idea of using my laptop as a music server, even though that is not the reason I decided on an outboard DAC. Just want to improve the sound of my CDs since I listen to a lot of vinyl, but also have alot of great CDs.

Hi Moofoo, here's some followup. Redbook CD playback, Cary Xciter vs. Sony 5400es: (Caveat: my Xciter DAC was thoroughly broken in by the previous owner, but my new 5400es has been on for 200 hrs, played about 30 hrs.) At this point the Xciter DAC (using the 5400es as a transport via a 0.5 meter digital coax) is equally detailed and spacious but pleasantly smoother and sweeter than the 5400es built-in DAC. The Xciter just never seems to have any digital edge, whereas the (still breaking in) 5400es DAC doesn't produce quite the same feeling of "ease" while listening to RBCDs. According to some the 5400es requires a long break-in period, so it is likely to smooth out over time.
Xciter Toslink input: Tested via Samsung BDP-2500 BD player ouputting 48khz PCM > 0.5 meter glass fiber Toslink cable > Xciter. The Dolby Digital soundtrack on Diana Krall's "Live in Paris" DVD sounds better through the Xciter than I thought possible from a lossy compressed standard DVD soundtrack. The Xciter sounds deeper and more dynamic than the Samsung, which although it's an inexpensive BD player, uses the ESS 9006 DAC chip which is quite good.