Low cost DAC

Just got my Adcom gear back from cleaning and repair (GTP-500 preamp and GFA-555 amp). Source is an Onix XCD-88 CDP. Speakers (for now) are Pioneer SP-BS22-LR. in conversation with the repair guys, I asked if there was a way to run the audio from my Samsung 8500 Plasma (sources are Comcast cable box, Apple TV and PS3) through this audio system. They recommended a short toslink from the TV to a DAC to the preamp. They suggested a low-cost DAC from Amazon like the FiiO D3 or SMO Muse. Is there an alternative at or under $100 that would improve the sound noticeably both for TV and/or CD?
"sources are Comcast cable box, Apple TV and PS3"

I would just run some analog IC's from each of your sources to 3 line level inputs on your preamp.
+1 Zd542 I highly doubt you would hear an improvement using a low cost dac in this situation.
Thanks for the responses. Sort of what I expected. The Dac in the Onix is a Burr-Brown, so it will serve for music. If I run analog IC outs into my preamp, but continue to connect them to the TV by HDMI, do I just turn the TV volume down or mute the channel to prevent the TV speakers from playing at the same time as the stereo?
Should be able to turn the TV speakers off using the TV menu options.