Supposedly you're using the mini-dock port replicator 2504 as this model has a S/PDIF port (the T60 itself and mini-dock model 2505 lacks the S/PDIF port).
The built-in audio device of the T60 supports for both loudspeakers and s/pdif: 48 Khz, 24 bit (maximum).
You can check it out yourself (in W7):
- Start > Cofiguration panel > choose Sound > Properties
If you're using JRiver Media Center as Audio frontend, set the output-mode at WASAPI-Event Style, set sample rate in this software package at 48 Khz and bitdepth resolution at 32 bit. You will enjoy an excellent musical experience.
If you insist on a higher than 48 Khz sample rate, then you'll need an external USB DAC amplifier such as f.i. FiiO E17 Alpen.
T60, 2008ZWA: T5600 CPU, 15" SXGA+ 1400x1050 IPS (LG) LCD Panel, ATI X1400 128 MB, 2x2 GB DDR2 RAM, 240 GB SSD OCZ Vertex 2, bluetooth, IR-port, Intel 3940 wireless 802.11 abg, Intel 1000 PL LAN card, NO fingerprint reader, Windows 7 Enterprise 32-Bit