Theta Jade or Basic II

Both are very similar - excellent base, dynamics, transparency, detail and cost far less than other transports at their performance point. The Jade is, to me, a little better...probably because it puts out less jitter and it's a later generation design. Also, there are instances of mechanical issues with the Basic's drawer assembly and laser tracking system. Overall, I would go with the Jade hands down.
If you really want to get the best out of the Gen Va and are not willing to go in the Levinson 31.5 altitudes, the Levinson 37 or the CEC TL-1 will give you exceptional performance and out-perform the Basic and Jade. I have a TL-1 on my Gen Va.

I run a Pearl with my DSPro Basic IIIa. The Jade is similar but more sophisticated. They both use the well regarded Pioneer Stable Platter mechanism (the little turntable platter that the disk rests on with the data side facing up), but doesn't your Miles as well? The Jade goes a step further than other Theta CD transports by employing a digital buffer circuit at its output to lower jitter levels going into the DAC. I think my Pearl sounds great, certainly better than the players I was previously using as transports (none of which was as good as your Miles), but I've never heard the Jade, and its been so long since I've heard a Basic II I couldn't make a comparision. I send the signal from the Pearl through a Monarchy DIP for jitter reduction, which I like the results from, but the Jade may not require that. The Jade should in theory sound the best, but it also seems to go for around double what many Basics are listed at. The possibility exists, however, that the Basic might not even be as good as the Miles you already have. Use the balanced AES/EBU connection on XLR for best sound, if you don't already.

I owned both and always thought that the Data Basic II was the better of the two units. I thought the bass was better with the II than the Jade. I always regreted selling the II for the Jade. The Basic II was just more musical. Good luck.

I use the Basic II with the Gen Va balanced. My brother bought a Jade and we compared the two at my house and his. He immediately sold the Jade. 'Nuff said.