I second the vote for Mytek ADC...
Depending on budget get the Stereo192 or Stereo96...
Another choice and the main competitor for Mytek, is Lavry with the AD10 and AD11.
Due to cost constraints, I went for the much more economical (like $250) eMu 1616m - which was a very substantial upgrade over my previous M-Audio Audiophile 2496.
I have also found, that the most transparent sounding resolution tends to be 24/96 and NOT 24/192 - I feel that 24/192 appears to push the gear to the limit of its capabilities, whereas 24/96 is right in the "sweet zone" - I have no more technically rigorous explanations.
My measurements with RMAA, also appear to show reduced distortion and improved linearity at the 24/96 resolution (although the differences are very small, so may not be reflecting the audible variation...)
The eMU 1616m and 1820m are now discontinued - but you can still find stock of them or used units out there. (they require a PCI slot in your PC, so not an option for a laptop)
They are very well regarded in the Semi-Pro or Home-Studio field.
The Mytek & Lavry ADC's are a notch higher, and are used by quite a number of studios and other pro environments. (you don't hear about them much in audiophile circles)
The nearest audiophile equivalent to the Mytek and Lavry is the Benchmark ADC - which also competes with them in the pro space.
bye for now