Be aware that opa627's are fairly expensive opamps, and are most likely fake if purchased for $7.50.   Here's a Head-Fi link that goes into great detail: http://www.head-fi.org/t/316937/fake-opa627s-in-the-wild   The ones straight from Maverick would be a great option.

I saw a thread (on Audiokarma: http://www.audiokarma.org/forums/showthread.php?t=489142 ) mentioning an adjustment that Grant Fidelity suggested if one intended to use the TubeDAC-09 as a Pre-amp (...

http://www.mav-audio.com/base/product/d1p   Looks like there's a new D1 "plus" model. Includes "up to 24bit/192khz digital audio support, Tenor 7022L pro audio USB interface and improved circuit design." It seems like a substantial update for $10 extra.