Seeking lower cost alternatives to Berkeley Audio Design Alpha USB converter


I am looking for a USB to optical audio converter.
The Alpha USB from Berkeley Audio Design is an external asynchronous USB to S/PDIF (or AES) interface. It's strictly a D to D converter accepting USB digital audio input and delivering digital audio output.
That's the type of product I'm looking for. However, at $1,895 the Berkeley Alpha USB is far more expensive than most similar products I've seen. Some of these products sell for less than $100.

I'm on a budget. Can anyone recommend one of the lower priced alternatives to the Alpha USB from Berkeley Audio Design?
lowoverdrive
@soix

> the Singxer SU-6 looks to be of good quality and is quite a bit cheaper than the Berkeley at $690.  

Yes, that looks like an interesting choice.
From your tip, I also found: 

- GUSTARD U16 around $300 
- Singxer SU-2 around $430 
- Singxer SU-1 (used) around $225 
- MATRIX Audio X-SPDIF 2 around $440 
 
Anyone know of others I should consider? Is there any clear winner among these?

I'll be search for reviews myself while waiting for any replies.
The Matrix X-SPDIF 2 does an amazing job. I used it to convert the usb from my desktop prior to the DAC. Worked seamlessly, many connection options and sounded amazing.  There are some measurements of this unit on the web that show it to perform very well in this application.
@fuzztone - thanks. I just ordered that. At that price I had to give it a try. Have you used it (or know anyone who has)?
@bk12 - I ordered the Matrix X-SPDIF 2 as well. I'll give both a try.