Well 'break the bank' is rather subjective, but I just went through this same experience. I recently bought a Bel Canto Dac 3 and I was not thrilled with the toslink connection from my SB3 compared to a Modwright CD player I have. It seemed a little thin. It was much better than the SB3 directly into my integrated amp, but still thin compared to the CD player.
I was poited by an audio friend to the Sterevox line of digital cables specifically the newer XV2. At ~$160 not an overly expensive cable new and I was able to buy one used for less than half that. Honestly I haven't received the cable so I can't speak from experience, but if my friend recommends it I am sure that I will be very pleased. If you're in no hurry I'll give you my impressions as soon as I get the cable and can compare. Meanwhile you could Google up the cable and read some pretty nice reviews that are related to the Slim Devices/Logitech gear so it's comparable to your proposed setup and is to mine as well.
Cheers and happy hunting,