I have used Mullard CV4003 in my TADAC. I bought them from upscale audio. this is their page for CV4003 with reviews at the bottom of the page. I am not good at writting what I hear so the reviews echo my own feelings on these tubes.
http://www.upscaleaudio.com/product.asp?itemid=12&catid=44
http://www.upscaleaudio.com/product.asp?itemid=12&catid=44