I had the TubeDAC in my system last weekend. It's a nice unit. I found it to be a touch tipped-up in the treble, which might be just the ticket in some systems. The owner of the unit said he thought the extra sparkle was an intentional design choice.
In my system, I prefer Red Wine's Monica. It is more balanced to my ears, though some might find it to be rolled off in the treble.
I do think either unit would be an affordable, effective upgrade for most CDP's
I also have use of an Ack! dAck 2.0 for the next couple weeks. I'll post findings when I have something to report.
I have an MHDT Laboratories Dialogue II non-oversampling DAC that I am liking more every time I listen. At the moment I'm only using a Philips DVP642 as a transport but I'm hoping to find a better DivX capable DVD player with a decent transport soon. Unfortunately space is limited so using a dedicated transport for CD's is kind of out of the question at this point. I bought the Dialogue II more on a whim than anything and it's really captivated me, easily one of the best $225 I've spent in audio.
I too ended up selling my MiniMax CD player in favor of the non-oversampling DAC. My system is heaphone based so moving from the MiniMax to the Dialogue II allowed me to add on a Headamp GS-1 heaphone amplifier/pre-amplifier for an overall system upgrade without costing much in the difference. I love the MiniMax and still think it offers great value but there's just something about the non-oversampling sound I can't resist.
I'm very much interested in trying more non-oversampling DAC's of the cheaper variety at some point as well. I know of the DAC-AH, Moodlab, Monica2 Kit, etc. I've been especially interested in the Monica2 but am not so confident in my DIY skills. I was not aware of the Red Wine option until I saw you mention it and I did a search. It looks very nice except I'm not sure about the battery powering, do you happen to know of anyone else that offers completed Monica2's?