Well, this ain't gonna help much with your specific question, but I own the Basic IIIa (the version to get if at all possible, and make sure it has the balanced I/O jacks for XLR connection - they sound better than RCA I/O if you can take advantage of them). This is a great bargain in DAC's today for a product that was a perennial favorite at around $2,700 when new. It is not for those who want a DAC to make their CD's sound 'more tolerable' in that it won't warm over the mastering flaws on disks, but if you want a machine that will accurately reveal what is on the disk, this one will do the job.
Full frequency and dynamic range, tonally neutral, big soundstage with solid images, high degree of transparency and fine resolution, articulate of subtle shadings, never flat, grainy, or dull. It's not designed to sound 'liquid' or 'musical' playing CD's that weren't recorded or mastered that way, with the result that it will sound very natural playing your good CD's, and let you know exactly what's going on with all of them. Common bugaboos: the source selection buttons and associated LED's are often schizophrenic, jumping around to different settings before locking-in, and the LED's can also sometimes light up in a ghostly fashion after the unit has been 'turned off' (in reality, it's always on stand-by - touching a button to drain away a static charge usually dims the lights).
Theta is very good company to deal with, both for service and for advice - even concerning their discontinued models and used gear - and the unit can be given a fix if it really fails to lock too frequently. Also features a handy digital recording loop-out w/monitor function and a polarity-inversion switch. My Basic blew away an upsampling MSB Gold Link w/P1000 I bought to check out the hype, even though it's 'just' a 18/44.1 machine with good old 8X oversampling and will only decode regular CD's. The secret is in Theta's balanced circuit design and implementation, plus their proprietary software-written digital output filtering, which preserves the analog signal's integrity in the time domain.
Competent as the unit is by itself, I've found it sounds even better when fed balanced AC if your PLC is capable, and can benefit from the addition of a good jitter-reduction box in between it and the transport (needless to say, it's very revealing of transport quality too - I use Theta's own Pearl together with a Monarchy DIP). Wish I could say how it stacks up against a lot of the other, newer DAC's out there that don't cost too much more new than a IIIa does used, but the Basic's sound hasn't given me any cause to want to look around further.