I am a Modwright Transporter owner..in fact the first. Dan and I collaborated on the design (basically I turned Dan onto the stock one, since I was a huge Modwright customer and early beta field tester), and once he saw the huge real estate he had inside the stock one he went crazy.
Check the 6Moons review for pics of before and after, and a few of my beta comments (as ted_b).
I owned the stock TP for a few months before Dan took it and did his incredible magic. The transformation from a player that had great detail and great bandwidth (with no ability to manage that bandwidth) to one that was toe-tapping musical and tight, powerful and full of air...was a transformation that I'll never forget. I've owned or own several of his modded universal players, but the changes that occcured from going stock to Modwright (MW) was phenomenal. The midrange became organic, the tonality of instruments was glorious, and yet the incredible detail that the AKM dacs brought to the table were left intact (realize the mods are, of course, after the DAC). If you look at the before and after pics you'll see an increase of probably 20x in hi-end componentry, the largest being his huge power supply components. In fact, Dan had me and the gang (we now have a few of us field beta testers) test his newest mod, what is being called the hypermod, only a few months ago, and it was released to production in the fall. It takes what Dan's learned from his award-winning PS 36.5 separate dual mono power supply design (for his flagship preamp) and use it, albeit solid state, in the Transporter upgrade. Sensational weight and dynamics were added to an already industry-strength music streamer and tube DAC (the TP has separate digital inputs so now it;s a tube DAC too).
Bu don't take what I'm saying as gospel...heck, I'm a huge Modwright fan (but not an employee or partner). Go to his mfg circle on Audio Circle and read about all the successes folks have had doing tube rolling (it has one 5AR4/5UGB rectifier and two signal tubes)and repalcing other transports and CDp's with it.
I had Wayne of Bolder Cable develop an octal adapter (the Modwright TP has a pair of nine pin signal tube sockets) so now we're rolling 6SN7's to our hearts content. My current favorite combo is a Mullard 5Ar4 fat base (even over the metal base) with a pair of RCA Silver Label 6SN7GT's. I have the new EML mesh plate 5U4G monster bottle coming next week and look forward to eval'ing it.
Net/net, the stock TP is nice, but most importantly, it is built to a level that supports additional investment...a solid foundation with a good hi-end DAC chip and solid well-built connectors, etc. Something the Duet,Sb3 or other low-priced streamers can't claim.
Also, If you're gonna go the external DAC route I'm not sure why you'd spend the $1500-$2k for a TP to feed it.
Ted