I've been living with the CD3 for close to a year now, just thought I update with more thoughts:
I like the CD3 quite a bit, gives a little tube coloration when I'm in the mood for it and provides a little bit of gain.
I gives me a little color when I want it in front of my O2 amp (the O2 purity fanatics will probably pounce on me for this statement).
I'm currently using it with the Black Treasure tubes and feel it a major step up from the stock tubes which were not to my tastes.
To be honest I don't know if the capacitor mods were worth it. If I had to do it over again I just swap tubes first then if I wanted more I would increase the value of the input caps.
I have only a few reservations, non of them deal killers:
1. It's not a true by pass when powered off. When the unit is switches off it is suppose to pass signal. This signal still has to run thought all the circuitry in the CD3, this eats of a lot of gain and I think may even affect the sound slightly. I was planning on adding a manual by pass switch to avoid this.
2. Extra gain. I'm divided on the fact that the unit adds some gain. Most of the time I love it, there are times I wish it would just have unity gain like a true buffer.
3. I wish it had more outputs. I will probably add this in the future. I guess the extra signal gain would be a plus for this mod
(see I told you I was divided)
I got mine for under $200 shipped from China on ebay. I got here in less than a week! You would be hard pressed to build anything for less money.
A better but much more costly DIY alternative would be an glass jar audio's BCF and ACF-2 kits:
http://glass-ware.stores.yahoo.net/acpcbocandus.html
http://glass-ware.stores.yahoo.net/bcf9pinpcb.html
After the cost of parts, power supply, and case I'd be looking at at least twice what I paid.
I think that a lot of money for something as simple as a tube buffer, I'd rather just build a OTL amp instead.