whats the budget ?
on of the most VFM and really good external SC's you can buy is the emu 404 USB (cost 200$ shipped in CONUS)
however wouldnt you like to look at better speaker chices than bose?
(if its more movies that intrest you than music i canunderstand your choice of speakers though)
in that case you can get pretty much any SC card depending on how many channel outs you need