There's more to converters than just sample rate and bit depth. No two converters sound the same any more than any two EQs or compressors sound the same.
Things like sample rate accuarcy, low jitter rates, word length conversion algorithms, quality of the circuitry on the analog side of the conversion, etc. all come into play. A great quality converter can do more for a signal's clarity, sharpness and lack of "digital feel" than almost any other device in the signal chain, regardless of the quality of the signal going into it.
Sample rates above 48kHz, OTOH, often have an unpredictable impact on the quality of the signal, with the positive impact decreasing with the decreasing demand of the signal. For example, 96k has it's greatest potential with more "organic" content such as classical and acoustic material - and even then the topic is a constant source of bar room argument amongst golden eared audiophiles; but it's advantages on a black metal recording are almost universally considered as questionable at best.
But very few will disagree that the difference between an Apogee converter and an m-Audio converter is readily audible even to the average ear regardless of whether one is listening to Yo Yo Ma or Steve Vai.
G.