The Weiss Vesta or INT202 will give you Firewire in and XLR or coax out. The Weiss Dac2 or Minerva will give you that plus they are also DACs. Friendlier than traditional pro gear.
On the budget side, you could try the TC Electronic Konnekt units or the Focusrite stuff.
You could also go with a USB to S/PDIF converter that handles hi-rez, such as the units from Empirical Audio, Bel Canto, Wavelength, and AR-T. 24/96 currently, but look for support up to 24/192 in the coming year.